Robocall blocking report reply comments

Comments were filed by 33 organizations, with a total 215 page of commentary. We’ve summarized it for you.

We noticed a few recurring themes across these comments:

  1. Industry associations representing high-volume callers are reporting problems with their calls being mislabeled or erroneously blocked.
  2. Voice service providers say:
    1. They provide ways for callers to report what they believe to be mislabeled or erroneously blocked calls,
    2. They have low false positive rates,
    3. Some callers are not following best practices. For example, some use invalid calling numbers or the same number for different purposes, which will cause their calls to be blocked or mislabeled.
  3. Analytics providers report very low false positives. They also mention high-volume callers who experienced trouble because they were not following best practices.

This round included an interesting proposal that the FCC should only allow blocking and safe harbor for calls that are fully authenticated using STIR/SHAKEN but then fail STIR/SHAKEN verification. This assumes that illegal robocall perpetrators will somehow attempt to sign their robocalls.

But without the proper certificates necessary to sign calls using the SHAKEN PKI, that would be a complete waste of time.

Robocallers and fraudsters tend to stop trying things that don’t work and move on to something else. A proposal to only allow blocking of such calls is essentially a proposal to disallow any robocall blocking or safe harbor for robocall blocking.

Summary of comments filed

Here are summaries of the comments filed. If you’d like to read the full document, click the company name in the header above each summary.

ACA International

  • Cited Accounts Receivable Management Outbound Calling Study by Number Sentry:
    • 21.3% of calls studied were blocked and 25.7% were labeled
    • 24.2% of the labeled calls were mislabeled
  • Service provider notification and recourse for blocking and labeling are inadequate
  • Objected to broad safe harbor
  • Urged the FCC to collect more data from service providers
  • Urged the FCC to either rescind the Call Blocking Declaratory Ruling or limit it to illegal calls

ACI – American Consumer Institute

  • Cited a study that found that reducing collections calls increases the number of debtors who go more than 90 days past due by 50%-70%. This harms their credit score, with adverse impact on insurance rates and getting hired for some jobs.

AICC - Alarm Industry Communications Committee

  • AICC has received reports from several alarm companies that calls from central stations have been blocked or mislabeled as potential fraud, spam or scam likely.
  • Urges FCC to adopt a Critical Call List of numbers that may not be blocked, including central station numbers that respond to alarms.

AFSA - American Financial Services Association

  • Legitimate calls are being blocked.
  • FCC should require voice service providers offer a challenge and redress mechanism so valid callers can have blocks lifted.

AT&T Services

  • When a blocked suspect robocall line calls AT&T’s Mobility, U-verse, Prepaid, or Cricket customers, the caller receives the following announcement: “Your access to this network is restricted. Please contact 1-888-212-6040 if you feel you have reached this recording in error.” The same message repeats in Spanish.
  • AT&T estimates that the false positive rate for its global fraud program is orders of magnitude less than one percent.
  • Out of approximately 30 telephone numbers that were the subject of complaints since AT&T launched its caller announcement, 27 of the complaints were deemed unsubstantiated upon investigation and, as a result, the telephone numbers remained blocked.
  • With an appropriate call blocking safe harbor, AT&T could more aggressively target and eliminate illegal calls on its network.


  • It’s premature to adopt safe harbor for call blocking tools that are not well understood or standardized across the industry.
  • Bandwidth is concerned that end users that rely upon IP-enabled services that incorporate underlying PSTN functions risk having their traffic improperly blocked or discriminated against.
  • Ensuring that illegal robocall prevention coexists with effective traffic delivery of legal calls across the communications ecosystem will depend critically upon the adoption of a set of additional supplemental standards and best practices to the current SHAKEN/STIR specifications.


  • Expect to use call analytics in conjunction with call authentication and attestation for expanded network blocking and consumer blocking and screening.
  • CenturyLink provides blocking on opt-in basis only because it’s new technology, potential for false positives, and lack of safe harbor.

Charter Communications

  • Will use call analytics and STIR/SHAKEN call authentication to identify known or likely nuisance and fraud callers and block them accordingly on an opt-out basis.
  • Additional tailored blocking will be available on an opt-in basis.

Cloud Communications Alliance

  • STIR/SHAKEN progress has been limited to the most straightforward use cases involving calls involving customers making calls using numbers assigned by the originating carrier.
  • Implementation has not involved more complex use cases, especially those involving enterprise customers. Use cases include:
    • Over-the-top VoIP provider uses numbers obtained from a carrier partner
    • Enterprise uses multiple least cost carriers
    • Enterprise has legitimately spoofed the number
  • Little progress has been made in finalizing standards to address enterprise calling use cases.
  • Industry has not coalesced around a standard for enabling transmittal of SHAKEN/STIR information across TDM networks.
  • 25% of the enterprise market is served by cloud-based communication services. There’s no reason why these providers cannot be appropriately vetted and allowed to sign calls.
  • A redress mechanism should be required of all entities that block calls and should be required for obtaining safe harbor protection.

Comcast Corporation

  • Implemented STIR/SHAKEN for residential, small business and medium business customers.
  • Implemented edge blocking for DNO and invalid/unallocated numbers.
  • Offer optional call blocking tools to customers.

Cox Communications

  • Detecting illegal calls is difficult, if not impossible, because carriers don’t know the intent of the calling party. However, the variety of tools available today have been effective in beginning to mitigate robocalls.
  • Callers must have access to redress mechanisms to rectify inadvertent blocking.
  • Broad safe harbor should be available to encourage the deployment of call blocking tools.

Credit Union National Association

  • Urge the FCC to require adoption of an automated SIP response for call blocking.
  • Urge the FCC to mandate redress mechanisms for erroneous blocking and labeling.


  • Robocall blocking is working
  • Voice service providers and analytics providers are working to prevent overblocking
  • Redress processes are available (provided a list of redress information for wireless providers)
  • Broad safe harbor would encourage service providers to use more innovative tools to protect consumers
  • FCC should avoid further mandates, such as additional reporting, whitelisting numbers, or notifying blocked callers, that would help robocall perpetrators figure out how to circumvent blocking.

Encore Capital Group

Encore Capital Group, urged the FCC to:

  1. Mandate a national call authentication and blocking standard for tier 1 providers, tier 2 providers, cables companies, and third-party apps
  2. Ensure that callers receive immediate notification when blocking and labeling occurs
  3. Create a single whitelist database
  4. Create a platform for blocked callers to request their legitimate calls unblocked, with expeditious response within 24 hours
  5. Create a national dispute platform that includes:
    • Consistent process for callers to appeal blacklisting of legitimate calls
    • Expeditious response within 24 hours
    • Universal standard for providers to grant or deny appeals.

First Orion

  • Intercept tone or message when a call is blocked is not easily done across the network due to equipment inconsistency. Also, such indicators would make it easy for the perpetrators to know they’re caught and switch to a different spoofed number.
  • False positives and false negatives have been running at a fraction of 1% of calls analyzed.
  • DNO blocking is limited by a lack of participation and data sharing.
  • High volume callers have been reluctant to register their numbers, engage in testing, and collaborate to improve the ecosystem.


  • Concerned about the risk of false positives if calls were blocked on opt-out basis without safe harbor.


  • Provides call blocking tools on an opt-in basis.
  • No plans to offer network-level call blocking.
  • Working on STIR/SHAKEN.


Urged the FCC to:

  • Support the creation of a common neutral reporting service for consumers and callers to report analytic service errors
  • Support the creation and adoption of priority call indicators for emergency services
  • Connect analytics service providers with real-time line number allocation status at no cost.


  • Call blocking tools are getting better
  • Today’s implementation of the DNO list is limited in reach and effectiveness.

Noble Systems

  • Being unable to know for certain whether a call was just blocked has been a persistent problem for callers. Some carriers provide a busy signal, which causes contact centers to reschedule the call.
  • When a call is blocked, a recording should tell the caller so and provide a number to call if they think the blocking was in error. A SIP error code should be returned with call block information.


  • Provided specific answers to questions from the FCC.
  • Provided an interesting summary of monthly landline statistics from October 2013 through January 2020.

RTI International

  • Erroneous blocking and labeling hampers RTI’s ability to make calls as a federal government contractor.
  • FCC should require clear procedures for redress of improper call blocking.
  • FCC should revisit the Declaratory Ruling and end the use of error-prone blocking technologies.
  • Federal callers should be eligible for any national white list or critical calls list.

Sirius XM Radio

  • Sirius XM is concerned about false positives, over blocking, and lack of redress mechanisms.
  • FCC should require carriers to provide an audio intercept and SIP error code to inform the caller that their call was blocked and whom to contact to seek redress.
  • No safe harbor protection should be available unless these requirements are met.


  • Sprint offers customers app-based call screening tools.
  • Has not implemented network blocking by default.


  • Urged the FCC to develop a robust safe harbor that’s technology agnostic and allows both reasonable analytics and STIR/SHAKEN authentication as well as future innovations.
  • The term “reasonable analytics” should be elastic to allow providers to use the latest analytics.
  • Suggested ways to measure effective blocking:
    1. Percentage of calls that are analyzed/verified/labeled/blocked
    2. Service provider customers that have call assessment tools available, regardless of devices, plans or network connections, as a percentage of total customers.
    3. Accuracy of call treatment (relies on customer input)
  • T-Mobile disables call blocking for a period of time for numbers that have called 911.


  • FCC’s failure to define “unwanted” calls has given voice service providers excessive discretion to determine what calls are unwanted
  • Service providers must provide notice of the blocking
  • Any potential safe harbor must provide callers with effective recourse to remedy mislabeled or incorrectly blocked calls

TDS Telecommunications

  • Implementing call analytics
  • Inclined to use an opt-out approach
  • Will evaluate to finalize decisions on blocking

Transaction Network Services

  • 0.2% of calls originating from high-risk calling numbers were falsely labeled as negative calls in 2019-20.
  • Failure of legitimate callers to follow best practices, such as using numbers for a signe purpose, avoiding calls at strange hours, and avoiding repetitive calls, contributes to negative scoring and potential claims of misclassification.
  • There have been cases where outbound calls from emergency services centers used an invalid calling number. They should use valid calling numbers, even with legitimate spoofing.
  • Supports creation of a Critical Calls List.


  • Supports blocking calls with complete attestation information that fails STIR/SHAKEN authentication.
  • Supports limiting safe harbor to blocking of calls with complete attestation that fail STIR/SHAKEN authentication.
  • Urges the FCC to proceed with caution in considering other forms of call blocking.
  • Urges the FCC to encourage and facilitate adoption of redress mechanisms for erroneous blocking or mislabeling of calls. These mechanisms should include:
    • Immediate notice using an error code or intercept code
    • Single point of contact with each voice service provider for callers to contact if they believe their calls are mislabeled or erroneously blocked.
    • Voice service providers, or their analytics companies, should be required to fix an error within a reasonable time period. Twilio suggests between 3 and 24 hours.

U.S. Cellular

  • Have provided call blocking apps to their customers.
  • Expect to start network blocking in mid-2020.


  • A broad and robust safe harbor provides greater incentives for voice service providers to block suspected illegal or unwanted calls.
  • Voice service providers are sensitive to over-blocking and committed to quickly addressing any legitimate calls that do get inadvertently blocked.


  • Have provided a call blocking app
  • Have recently begun network call blocking of high-risk spam calls
  • The data indicate that Verizon’s call blocking algorithms are rarely wrong when identifying spam calls, but they let through more spam calls than Verizon and their customers want. False positives are low, false negatives are higher.
  • Verizon sends a Release Code 603 (“denied”) for calls blocked in the network.
  • Verizon does not send intercept messages for calls blocked through their Call Filter app. Such calls are actually terminated to the device, then sent to voicemail.
  • Verizon does not want to help illegal robocallers game the system by sending them an intercept code, which they would use to then switch their autodialer to use another spoofed calling number.
  • Verizon has noticed that a substantial amount of traffic that does not appear to be illegal is sent with invalid calling numbers. Educating callers about the blocking of invalid numbers is important.


  • Vonage does not plan to block calls based upon reputation scores. They are concerned about the lack of legal clarity regarding call blocking safe harbor.
  • The FCC should adopt a robust safe harbor to encourage carriers to provide additional call blocking
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