IAX PSTN Call Credit

Brilliant all round, and good value for money on calls to landlines the world over. Extremely useful and call set up is very quick to land lines.
However calls to mobiles in some countries is shocking, poor quality and sometimes you're lucky if you even get connected. I notice that in some cases, the the channel is answered before one hears ringing, so ones account ends up being debited even though the call is not sucsesful.