Wifi kills 3G requiring reboot. iPhone

Ive had my 3GS since July 2010 and have chronic battery and wifi/3G issues.
About 50% or more of the time when I turn off wifi, 3G wont connect until I reboot the phone (3G shows up but no Internet connection). I have a small data plan so I use wifi all the time at home. But if I dont turn it off while at work all day my battery will drain to zero.
This has been going on since I first got the phone so I dont think its iOS related. At first I was using my really old old SIM (7 years) and had it replaced. It was a little better, but still happening so I took it to the apple store who replaced it free/direct exchange. Problem is still happening and Ive had the new phone for 8 weeks.
Could the replacement SIM be bad causing wifi issues and battery drain? Aside from the wifi/3G issue, I have to turn off all extras (push, location services) or my battery drains 10% an hour when just in standby.
Im desperate! Anyone have a suggestion?
3GS iOS 4 New phone as of January 2011