In the last week I've noticed that my service near Oak Park, IL has begun to wildly fluctuate. It goes from 3G to E and back again in 15-20 sec. And yet I have full bars on both. It's really annoying. I haven't been able to test this anywhere else yet, but I'm curious if this sounds like a phone issue or a cell tower issue. Any recommendations? I just updated to the latest firmware (2.2.1) but the problem continues to persist.