Details of AT&T's Femtocell Slip

Ok I will just be giving you a simple idea of what this does:

The use of this tech is allowing you to talk where the voice is not working to well, Just like verizon/sprint/tmobile its allowing you to pick up signal where you would be able to before. Therefore VOIP is the honestly only way you are going to work it, 3g is going to make the battery drain faster but not as fast as using the phone on a weaker signal.

To be honest I would bet that your life of your battery will actually be better once you get one of these.

Less strain trying to get better coverage=better battery life.