Can you tell us how the VoIP trunks are being used? Explain all the possible ways calls are traversing these trunks? Maybe it's not the trunks, but how they are used.. Had a similar situation where a remote office would forward their calls at night to an auto attendant via VoIP trunksk, they also used centralized voicemail... Since the lines were analog, and they were forwarding to an AA in another location, the caller would dial an extension that resided back on the other side and it would freeze up the trunks.. Found that since the first trunks are "Public" and then the remaining are "Private", it would never release the trunks when the caller hung up. We forced them to use the AA at their local side, then it would transfer to a local extension and forward to the centralized voicemail across those VoIP trunks and it worked well..