Every Calilio-issued US phone number now carries A-level STIR/SHAKEN attestation by default. No configuration required, no extra cost. This change rolled out gradually over the past two weeks and is now active on every active and newly-provisioned US number on the platform.
What this means for inbound answer rates
STIR/SHAKEN is the framework US carriers use to verify that the caller ID on an outbound call has not been spoofed. A-level attestation is the highest tier: the originating carrier asserts both the caller's identity and their right to use that specific phone number.
Calls that arrive with A-level attestation are dramatically less likely to be filtered, marked as "Spam Likely", or blocked outright by the recipient's carrier. Most studies put the answer-rate lift between 15 and 30 percent for outbound sales calling, depending on the destination carrier and the recipient's call-screening configuration.
Why this matters now
The FCC's 2025 enforcement updates raised the bar for carrier filtering. Calls without attestation, or with the lower B or C tiers, are now treated more aggressively by Verizon, AT&T, and T-Mobile. Carriers are not required to deliver low-attestation traffic at all, and many are choosing to filter it heavily during the day.
For Calilio customers running outbound sales or appointment confirmations, A-level attestation is the difference between connecting and being marked as spam.
What you need to do
Nothing. The change is automatic. If you want to verify, the dashboard now shows the attestation tier on every call detail record under the Compliance section.
If you are using a number you ported in from another provider, the attestation tier depends on the issuing carrier's STIR/SHAKEN configuration — not Calilio's. Numbers you port to Calilio inherit our A-level attestation within 24 hours of porting completion.
Where to learn more
The FCC robocall enforcement page and our own compliance documentation cover the framework in depth. If you have a question specific to your account, the compliance team responds within one business day through the in-app support channel.