Jeff has an unlocked GSM phone which he uses via TracFone, but it doesn't get data near his home. Leo says that part of the issue could be that TracFone has a deal with carriers that would make tower availability limited.
The chatroom says that AT&T stopped monitoring 3G signal strength, so his bars could be lying to him. Leo also says that his phone has a secret menu that will tell him more about his connection. It's a testing and diagnostic menu that will tell him what frequency and signal he's getting. Jeff can Google his phone to find the diagnostic menu. There are apps as well that can tell him more of that information, like SignalSpy or G-MoN. It may also be that the phone really only supports older frequencies, and with LTE, it's getting lost in the clutter.