I don't have 4g but I do have a dell streak with at&t that had this problem intermittently in my home, where I usually get 3g, but instead kept picking up edge, and only went back to H+ or 3G when I was in a different part of town. The way I fixed this was forcing it to use WCDMA. In your network settings, under network settings, it's set at a default of WCDMA/GSM auto. For whatever reason it kept choosing GSM (Edge speeds) so I changed it to WCDMA only so theres no band switching. It also saves your battery from not having to constantly scan and compare speeds between the two bands.