Follow the some troubleshooting steps. It may help you
-configured for ground start signalling
- used supervisory disconnect dualtone mid-call with the timeouts command:
-timeouts wait-release 5 and timeouts call-disconnect 5
- tried using a custom cptone defining the frequency
voice class custom-cptone 1
dualtone disconnect
frequency 480 620
cadence 200 200
- configured for supervisory disconnect anytone