Ok, I just got the iphone in december and have upgraded to 1.1.3

Now, I recently heard all about jailbreaking your phone. Although I hear that if you jailbreak or downgrade from a 1.1.3 you cannot use the phone part of the device anymore..anyway question is:

Is there anyway to get a working jailbreaker on my phone without screwing anything up?..please advise!!

I need help!!