The recent jailbreak and unlock method by upgrading the iPhone baseband to iPad 3.2.2 06.15.00 version and unlocking via ultrasn0w 1.2 has been reported to cause iPhone deplete the battery very fast and also making the device very hot when in use.
The official fix for this issue is not yet released and is being worked on. It will be released on Cydia when ready. Meanwhile you can try these methods to temporarily fix the issue.
1. Activate using official carrier sim
First way is to activate your iPhone using the official carrier sim card (AT&T). You don’t need to be in country where it’s service is provided. Only sim card is needed. Just put the sim in the iPhone and connect to iTunes. Let it activate officially. Once it’s activated, you can take out the sim card and use your own carrier sim.
2. Turn of 3G when done using it
Another temporary fix is to turn off 3G every time you are done using it.
Note that you can turn off 3G from the iPhone settings too but a better option is to install sbsettings and use it to turn 3G on and off.
This method is sort of tiring and irritating each time you use 3G service! and ofcourse, it’s applicable in countries only where 3G service is available.