iPhone 4 3G slowed down immensely all of a sudden

So I've been having issues with my 3G on my iPhone 4, I've restored with a backup twice, didn't change, I just did a restore to factory settings, I even reset my network settings multiple times, even went to AT&T and got a new SIM card, tried everything imaginable (I think). After all that it's still running slow. I downloaded the "Speedtest.net" app. Ran a couple of tests, I made a friend download the same app, he also has AT&T. I came up with 0.05Mpbs - 0.11Mpbs while he came up with 1.17Mpbs - 2.01Mpbs. Both on 3G, both on iPhone 4, both on AT&T, both in the same building. I have no idea what else to do, any suggestions?