provided by Star2Billing S.L.

You could purchase better quality termination from your existing carrier, or move to a carrier that doesn't suck quite as much.

Using A2B alone to work around this issue is possible by setting up a second identical trunk to the same carrier, and setting the first trunk to fail-over to the second. I don't think A2B will fail-over if the carrier indicates congestion, which many do when they can't route the call. I may be wrong on this point.