I contacted voip.ms' support, but they couldn't really help me. It often but randomly happens that I cannot hear the recipient's phone ringing when I make a call. The line stays mute until someone answers. Do you know what might cause this problem (which is fairly new -- maybe 1-2 months)?
I use a PAP2T with Mango's settings. I tried a few times to replicate the problem with X-Lite, but so far it doesn't occur with this program.