ok, sorry, i have misread your first post.
6 minutes in one cell ??
I’ve never came across anything like this. All calls on this cell are released after 6 minutes, exactly, 6 minutes ? All of them ?
What about GPRS transfers ? Can you try to do a FTP download for more than 6 minutes ?
Well, unless you have such weird timer in the BTS, I still believe it’s a MSC issue. Maybe I’m missing something, though. Which codec are you using? AMR? If yes..
Could you try using another codec?
Which vendor is it?