I have had AT&T prepaid service for almost 3 years now. And the past year has been the worst I've ever expierenced. I don't believe it's the device as I had two different devices with the same unreliable coverage. For hours sometimes 4-6 hours I will not have service, but without moving the phone's location, it will then have half to full amount of bars. And it's not a localized issue in one area. It's a problem no matter where I am in the city of Moline, IL. I could be at work and have a strong signal, and then like a light swtich, not have signal for hours upon hours. It makes me upset as I use my phone quite a bit for helping fellow classmates and I have a dropped signal for hours.
Anybody else have extremely unreliable AT&T gophone service? I want to change to Verizon if this keeps up, but I don't want to lose my number as well.
If I were you, I would check with other AT&T customers in your area (if there are any that you know of) and ask them how their service is. If it's somewhat good, then I would suggest getting a new SIM card.
It's also perfectly possible that AT&T may just have very poor coverage in your area.