A SIP AG is similar to a voice gateway connected to a PBX, and a SIP AG user is registered with the SIP server on the PBX. That is, the SIP AG user is similar to a SIP UE user on the PBX.
When a SIP AG user calls a PBX user, you need to correctly configure call prefixes. The inter-office trunk does not need to be configured.
Assume that a SIP AG user's number is 2200 and a PBX user's number is 1100. The local call prefixes 11 and 22 need to be set.
Check the SIP AG configuration.
Check whether the SIP AG interface configuration is correct and whether the registration status is normal.
Check whether the user configuration on the SIP AG interface is correct.
Check whether the FXS interface on the SIP AG is normal.
Check the PBX configuration.
Check whether the SIP server configuration is correct and whether the SIP server status is normal.
Check whether the prefix configuration is correct.