I'm trying to think of things that could go under the VoIP category for the likes of iTalk/VFX.

So far I've got:
* Phone doesn't ring.
* No dial tone.
* Calls cannot be connected
* Calls divert prematurely?
* Call too quiet?
* Key tones don't work

Anyone else have any suggestions (or able to put it in step by step)? As I don't have a VFX or iTalk connection, I'm only guessing that these are common issues.