I do apologise for the goof-up. My eyes were tired and blurry. I posted link to the post I was in. I have corrected the error, but it won;t help you with iPhone as it's T-mobile prepaid.

SO far, Straight talk is the only other operator other than those mentioned by Mr Bean, that I think will work with PCS and CLR bands (for iPhone)

If you have a GoPhone and an iPhone, AT&T reseelers (MVNO) are your best bet. I was looking for a no contract phone for my T-mobile service as I did not want to pay for a data plan every month. I tried T-mobile branded Dart, but did not like it. I have now bought a T-mobile branded Wildfire S (android phone by HTC) for $150, which is tolerable, but the screen is rather small. It works in 3G on AWS (Band IV for T-mobile) and IMT (Band I for most of Europe Africa and Asia) and got it unlocked for overseas use. I would prefer a bigger screen, but can't find anything better within my price range. Unless you like T-mobile and/or want to buy no contract T-mobile banded phone, your best bet would be to go with those mentioned by Mr Bean or StraightTalk.

I thought I saw something that indicated it works with AT&T 3G bands. I will check to make sure it does. StraightTalk is AT&T reseller or virtual network operator and it markets 3G phones that work on that network. My inference is that it will work on the same bands as iPhone does. Since your iPhone is unlocked, it should work unless there is some issue with iPhone that I don;t understand.
Disclaimer: I do not own, nor have I ever used, an iPhone.