Poor audio quality on some calls

I wanted to see if anybody else has experienced this issue:

We are running Asterisk 1.42 with FreePBX and are experiencing “bad connections”. The best way to describe this is that the quality of the call is immediately bad and does not improve regardless of the length of the call. If you disconnect the call and then dial the person back or have them call you back, then the call is crystal clear again. We have monitored all of the bandwidth and tested extensively. This is not a normal dropped packet or latency based call issue. There is “static” on the line like you would normally find in PSTN lines. I want to cover all of my bases before I go back to the provider (Vitelity), who has a propensity for telling us that it’s a problem on our side.

We’re using G711u.

There is no Asterisk 1.42.

Sorry. Asterisk