[Serusers] BYE submission by SER in case of mediaproxy timeout or credit limit reached. ?

Hello, I wonder if anyone has a solution for having a call being terminated by SER in case a certain credit limit has been reached or in case the connection was lost to either end of a call ? I am testing with mediaproxy and can have it timeout, it will tear down the RTP relaying nevertheless it wont teminate the actual call by means of a BYE request that was setup to the PSTN gateway. So this connection stays open. Is there a way to interface with SER and to have it generate a BYE to the PSTN gateway ? Can I use RADIUS to tear down the call in case of a prepaid credit limit ? Best regards Paul van Schagen