Can I jailbreak my iPhone 4 if its unlocked for t-mobile? - 1

I was wondering if I could jailbreak my unlocked iPhone 4? I use it for t-mobile and it is a gevey unlock. What is the worse case scenario that could happen? Would the gevey card stop working? If i could jailbreak my iphone 4 can you tell me how? And if you did it before what was your experience?

Even though jailbreaking your iPhone/iPod Touch is legal, you should have someone who has done jailbreaks to Apple products jailbreak yours. I had my boyfriend jailbreak mine, but the only bad thing is that trying to update your apps doesn't seem to work as well.

Worse case scenario that could happen?
A gevey sim is a hardware 'hack' which tricks the iPhone into making a call via a different route. You will never be able to update your handset if you use a Gevey Sim. Because they sit 'behind' your own sim, they are also prone to getting stuck into the iPhone forcing a trip to an Apple Store to take the phone apart and get it removed, which they now refuse to do and claim they void the warranty. Our method turns your iPhone into a factory unlocked unit, meaning you can always update to the latest version of iOS. Your iPhone is an expensive device, and you want to keep up with iOS updates as Apple brings out new features etc.
http://attiphoneunlocker.com/ No software unlocked in Apple's IMEI database
http://unlockiphone-4s.net/ Here is software you you can jailbreak then unlock.