I accidentally downloaded music on itunes and it completely messed up my previous jailbreak and unlock. I was running my iphone 3gs on T-Mobile but now it doesnt work, I rejail broke it and installed snowbreeze and also tried redsn0w, the jailbreak works again (meaning I can now download apps off cydia again) but the actual phone function isnt working on my phone, the sim is functional (Ive tried putting it in other phones and it works, but on my iphone it only has one little bar and all calls are failed and the texts dont send/receive either.

I am trying to use Tmobile on my phone
I am running version 4.3.3 (8J2)
my modem firmware is 6.15.00
and my model is MC640LL

have you tried installing ultrasn0w?

iClarified - iPhone - How to Unlock the iPhone 4, 3GS, 3G Using UltraSn0w