Outbound call centers are facing an increasing challenge: ensuring their calls reach consumers
without being blocked or flagged as spam. With the Federal Communications Commission
(FCC) recently passing new regulations requiring telecom carriers to send specific response
codes when blocking calls, call centers must adopt best practices to improve call deliverability
and maintain compliance. This blog explores the latest FCC ruling, the role of STIR/SHAKEN,
and how phone number registration and remediation can help outbound call centers achieve
better results.

The Latest FCC Ruling on Call Blocking

On September 26, 2024, the FCC adopted new rules to enhance consumer protection against
illegal and unwanted calls. These rules, effective January 27, 2025, require voice service
providers to send a Session Initiation Protocol (SIP) code 603+ when blocking a call based on
reasonable analytics (Federal Communications Commission). This transparency measure allows
businesses to understand when and why their calls are being blocked, giving them an opportunity
to take corrective action.

Additionally, the FCC mandated that all U.S.based providers in the call path must block calls
from numbers on a reasonable do-not-originate list, including unallocated, unused, or invalid
numbers, as well as numbers that subscribers have requested to be blocked.

Implementing STIR/SHAKEN for Caller ID Authentication

One of the most critical steps in ensuring your calls get through is implementing
STIR/SHAKEN, a framework designed to prevent caller ID spoofing by authenticating the
legitimacy of phone numbers (Federal Communications Commission).

How STIR/SHAKEN Works

  • Caller Verification: The originating service provider digitally signs the call, verifying
    the legitimacy of the caller ID.
  • Call Authentication: The call passes through telecom networks, where providers check
    its validity using cryptographic signatures.
  • Receiving Party Validation: The terminating service provider verifies the call before
    delivering it to the recipient, reducing the likelihood of fraud or spam labeling.

Impact on Call Deliverability

  • Calls from verified numbers are more likely to be answered.
  • Reduces spam flags from carriers and third-party analytics firms.
  • Enhances customer trust, as recipients see a validated business number.

Phone Number Registration: Ensuring Legitimate Caller Reputation

Another crucial strategy for avoiding blocked calls is phone number registration with major
carriers and analytics providers. This process involves submitting business phone numbers for
verification, ensuring they are not mistakenly labeled as spam.

Steps to Register Your Phone Numbers

  • Identify your primary outbound numbers and ensure they align with your business
    identity.
  • Submit your numbers to major call analytics firms such as First Orion, TNS and Hiya
    (First Orion, Hiya)
  • Monitor reputation scores regularly to detect and address spam labeling before it impacts
    your operations.
  • Use consistent business caller ID to maintain a strong reputation across networks.

Impact on Call Deliverability

  • Increases answer rates by reducing false spam labeling.
  • Improves brand trust, as customers see a registered, verified number.
  • Prevents call blocking due to suspected fraud.

Phone Number Remediation: Fixing Flagged or Blocked Numbers

If your phone numbers have already been flagged or blocked, number remediation services can
help restore their reputation.

How to Implement Phone Number Remediation

  • Identify flagged numbers using call analytics platforms or carrier feedback (TNS).
  • Submit a remediation request through analytics providers to correct false spam labeling.
  • Rotate flagged numbers and limit overuse of specific outbound lines to prevent repeated
    flagging.
  • Use call behavior best practices, such as proper dialing frequency and immediate agent
    responses, to maintain a positive caller reputation.

Impact on Call Deliverability

  • Restores flagged numbers so they are no longer marked as spam.
  • Improves connection rates for outbound calls.
  • Reduces carrier blocking, ensuring your calls reach the intended recipient.

Best Practices for Call Frequency and SIP Code Monitoring

How Often Should You Call from a Single Number?

  • Avoid making more than 100 calls per day from a single phone number (First Orion).
  • Spread calls evenly throughout the day to prevent sudden spikes.
  • Rotate phone numbers across different campaigns to minimize red flags from carriers.
  • Limit calling the same lead to 3 attempts per day and ensure proper spacing between
    attempts. Take into consideration any state dialing rules that may be applicable.

Monitoring SIP Codes and 603+ Responses

  • Regularly track SIP 603+ response codes in call logs to understand how often calls are
    being blocked.
  • A reasonable percentage of 603s should be under 5% of total calls (First Orion). If the
    percentage is higher, it may indicate an issue with caller reputation.
  • Investigate any spikes in 603 codes and take remediation actions, such as re-registering
    numbers or adjusting call behavior.

By closely monitoring call frequency and SIP response codes, call centers can make data-driven
decisions to improve call deliverability and reduce the risk of being flagged as spam.

Conclusion

With the FCC’s latest call blocking regulations in effect, outbound call centers must take
proactive steps to prevent their calls from being flagged or blocked. Implementing
STIR/SHAKEN, registering phone numbers with major analytics providers, and utilizing phone

number remediation services can significantly improve call deliverability and maintain
compliance.

By following these best practices, call centers can ensure their calls reach their intended
audience, enhancing both compliance and operational success.

How CallShaper Helps

CallShaper can authenticate calls with STIR/SHAKEN, register phone numbers for improved
trust, remediate any numbers that have issues, and track call deliverability to identify potential
issues. Combining these efforts can have a substantial impact on your contact rates—and
ultimately your sales!

Ready to improve your call deliverability and maximize your outbound success? Contact
CallShaper today to get started for as little as $5 per number!

Contact Us & Learn More

Sources

Disclaimer: The information provided in this blog is for informational purposes only and does not constitute
legal advice. Compliance regulations frequently change, and businesses should consult a
qualified attorney or compliance expert before making regulatory decisions. CallShaper provides
technology solutions to enhance contact center efficiency and compliance, but does not offer
legal representation or compliance certification.

AI Disclosure: This article was generated with the assistance of AI and reviewed by industry professionals to
ensure accuracy and compliance.