For all those who don't know how 2 and 3G works and why its best to make calls on 2G, here is a quick summary
3G and the way the cells work to accommodate data users to give them the best available ammount of bandwidth is a little unfair in my opinion (this will change with the introduction of LTE), but the cells are "flexi" or in another word, the shrink with useage, this means you may have a signal but the further you are away from the cell, the greater the chance you have of dropping off it, even if one minute you have a good signal and the next... poooft! gone
😞2G, the best way to make your normal phone calls
Really it is, LTE is partially based on this technology (where the cell area is fixed and not flexi like 3G) so that when your on there you wont get dumped off, so if your making lots of phone calls on your wonderful smart phone (and they are a real nightmare due to their software), switch to 2G only, if you want to go browsing then switch to 3G, don't just leave it on 3G or you will get dropped calls if it cannot hand over to a 2G cell (this happens unfortunately :()
Skype... I'm adding this one as lots of people seem to use it now, I personally hate VoiP, its a cheap and nasty (low quality and laggy) way of making calls, ok if you can live with it then use it but the quality can suck.
An example for this is a friend of mine uses skype on his (dare I say it, 3 iphone 4), he thought it was wonderful, said he had/has no issues with it, I said it sucked, bad quality, lag etc, to prove a point he made a call with me standing next to him and another friend there too, call made, I hear him speak next to me, 2 seconds later it comes through on the phone.... lovely lol.
Anyway back to the main topic, as above, 2G for calls, 3g if you want to browse.