Call is not disconnecting if ip phone is hangon

General Help
1

I have 2 channel SIP trunk of voip talk. I have configured these channels on free pbx and when agent hang up phone the call is not disconnected and if we try an other call. Call is not connected and message is played you are exceeding two co current call.

2

*hang on phone
I have 2 channel SIP trunk of voip talk. I have configured these channels on free pbx and when agent hang on phone the call is not disconnected and if we try an other call. Call is not connected and message is played you are exceeding two co current call.