While we shifted our office we got a new PRI line and after connecting and configuring this line we started facing this issue. When ever I make an external call the call is getting connected and the person at the other end is able to answer the calls however the issue is that we are not receiving any ring back tone while the call is in progress. The service provider already checked this issue from their end and confirmed that everything from their end is working fine. I was wondering if there is any option in Avaya IPO to enable and disable the ring back tone while making calls?