Originally Posted by PathFinder@9GS

I think what happens is that if you force your phone to 3G or 2G.. and it loses signal ..and there is a delay between the signal lost and the phone app actually knowing about it.. and because you select one mode (3G/2G) it cannot move over to the other band
and tries making a call while actually having no signal..

If you get the connection error .. Try switching between modes or just set it to "Dual"
I had the same problem.. I would just switch between modes and it would work fine after that.