Many people no longer answer calls marked “Spam Likely” or “Suspected fraud”, and phones increasingly show those labels automatically. If your business calls customers, you need to understand how those labels are decided.
Call authentication: STIR/SHAKEN
In the United States and Canada, carriers use STIR/SHAKEN, a framework that digitally signs each call to confirm the caller is entitled to use the displayed number. The originating carrier assigns an attestation level:
- A (full): the carrier knows the customer and confirms they may use this number
- B (partial): the carrier knows the customer but can’t confirm the number
- C (gateway): the call entered from elsewhere and can’t be verified
Calls with full attestation are far less likely to be blocked or labelled. Other countries are introducing their own caller-ID authentication and anti-spoofing rules.
Analytics and reputation
Separately, carriers and apps score numbers on behaviour:
- very high call volume from a single number
- short call durations and low answer rates
- many calls to numbers that don’t exist
- consumer complaints and “block” actions
A number with good behaviour builds reputation; a number used like a robocaller loses it quickly.
Practical steps
- Use numbers you own and that are registered to your verified account. Verification underpins attestation. See why operators ask for KYC.
- Send calls from the same provider that owns the numbers, where possible, so they can sign with full attestation.
- Keep volumes per number sensible and spread large campaigns across numbers you legitimately need, not disposable ones.
- Make callbacks work and answer them.
- Register your numbers with the carrier and analytics registration programmes that exist in your markets.
- Monitor labels. Test-call your own numbers regularly from different networks.
What not to do
Rotating through fresh numbers to escape labels, spoofing numbers you don’t own, and calling without consent are both unlawful in many places and the fastest way to have your numbers and your provider’s ranges blocked.
Frequently asked questions
Why is my new number already labelled spam?
Numbers are sometimes recycled. Ask your provider to check the number’s history, or register it with analytics providers.
Does STIR/SHAKEN apply to calls from outside North America?
Calls entering the US from abroad usually arrive with gateway attestation. Local US numbers from a US-connected provider give better results.
Read our Acceptable Use Policy