Agent get ring forever

[mav2287]

We are seeing something interesting that I think is a carrier issues. Hopefully someone has seen this before. VICIdial seems to work flawlessly, BUT every now and then instead of a person on the line in auto dial mode the rep will have a ringing sound. It beeps in and show as a live call, BUT there is no one there and it is just ringing. What makes it interesting is that ringing will last FOREVER I have sat on one for like 20 minutes and it just rings and rings. If you call it from a different carrier or something like your cell phone the number works fine. It may also work the next day just fine with the same carrier. I have also looked at the CLI and there is nothing out of the ordinary in the CLI. My thought is that it must be a carrier side issue, but it seems to happen more with some carriers and less with others. Anyone know anything about this or able to offer any help?