We have a customer with Charter service. Three T-1's bonded together via an Adtran router. They give us a single PRI on an interface card to connect to a Samsung OS500r2. This has been working well since June 2012. After the new year holiday the incoming calls are distorted one-way. Caller hears customer fine. Customer hears caller distorted. Outbound calls are fine both ways. Charter sees constant clock clips when we plug the OS500 into the PRI interface. They are hung up on this. They refuse to look further until the slips are minimized. Charter claims no software or hardware upgrades were done over the holiday. We have changed out the SMCP (processor) of the phone system - no go. I don't buy the clock clock slips as the problem. What do you think?