No busy tone from SBC to PSTN
Hello,
We just implemented CUCM-ISR-SD-ESR-PSTN scenario and running some test for SIP trunks from various providers.
One of the test requires that IP phone (single line) from internal network to send out busy tone to the PSTN caller when it is busy. As of now it just keeps ringing forever as for test I have removed the VM account. Please advise on the resolution. Thanks.