Line hanging for 2-3 min after an unanswered call

We have connected 4 telephones lines in the fxo port. For all the telephones line, if the calling party terminates call before pickup, specific telephone lines remain engaged for 2-4 minutes. So , new calls (incoming as well as outgoing ) will not be possible through this telephone lines for 2-4 minutes.

can anybody help on this???

Try searching the forums, here and elsewhere, for hangup disconnect supervision methods appropriate for four provider, there are a few hundred posts on that subject.