voice troubleshooting case debrief-FXO ports hang

Problem description:
FXO ports hang after PSTN to PSTN (hairpin) call forwarding disconnected by the calling party

Symptom:
When a call comes from the PSTN, the call is been answered and the user transfer it to another user through the PSTN line ( either to mobile phone or landline) . The established call occupies two lines (ports) on the CCM router. After the external parties hang up the lines, the router doesn't release the particular lines for further use.

Explanation:
On a transferred call the PSTN side is the originating side.If this side hangs up first without signaling the FXO on the CCM that the call is disconnected, CCM has no way to realize that the FXO ports should be released.

Action Plan:
1.applying the following commands to the voice-ports
supervisory disconnect dualtone mid-call
timeouts call-disconnect 5
timeouts wait-release 5
(this step has been done but it doesn't fix).
2.Please get the cadence and frequency of the disconnect tone from the telco.
3.Create a custom cptone if you can get the frequency and cadence from the telco and apply it to the voice port.
Sample configuration :
e.g. if the telco say the frequency and cadence they use for the tone disconnect are n1,
and n2 n3,respectively, then this what you will need to add:
voice class custom-cptone c-jason
dualtone disconnect
frequency n1
cadence n2 n3

Workaround:
If you can't get the required disconnect tone parameters from the telco,the only workaround is either reconnecting the cable from the FXO port to the or shut/no shut the voice-ports to release the engaged ports.