AT&T Synapse Common Issues
Unable to make calls after changing the calling number (outbound caller ID) on a registered SIP trunk
Note: This only applies if you are registering to
Clearfly requires that registered SIP trunks set their registration number in the P-Asserted-Identity (PAI) header if they are sending from a non-owned telephone number or if the customer wishes to preserve caller-ID on forwarded calls. More details are available in our FAQ.
Currently, AT&T/VTech does not support PAI assertion, so calling from a non-owned number is not supported via a registered SIP trunk on an AT&T Synapse system.