Ways to re-unlock a factory unlocked iPhone 4?

I just got a factory unlocked iPhone 4 and put my tmobile chip in and I keep getting an E next my signal at the top of the phone and i called tmobile and they said I won't be able to get 3G-4g because It is a factory unlocked phone and I didn't buy it from them. Is there a way to re-unlock it or another way to get 3G.

Sounds like its something the carrier has locked out, I don't think you can change this with your phone.

Factory unlocked iPhones can't be locked.

That T-Mobile rep clearly didn't know what he/she was talking about. Before T-Mobile announced the iPhone to be officially sold by them a couple of weeks ago they had estimated that there was over 1 million of them already on the network, which in most, if not all cases, had to be unlocked since T-Mobile was not an official carrier for the phone at that point.

The reason why you are getting E, which stands for EDGE which is 2G by the way, is because T-Mobile uses different frequencies for their 3G network than what the iPhone used, so the iPhone goes to the next one it could access that being the 2G/EDGE network. Been that way for years now.

They are however introducing iPhone friendly 3G/4G towers now that they do sell the phone officially so it would be a matter of time.