Iphone 5 iOS6 wont connect to 4G after "no Service"

I'm in a building all day that has little to mostly no service. My iphone is almost constantly without connection to any cellular network (At&t). When I leave for the day my phone will constantly look for a cellular network connection, but it ONLY find the Edge network and only does so briefly. It will then lose that connection then find it again, about every one to two seconds. The only way it will find a 4G/3G connection is if I turn on Airplane mode then turn it back off. I've tried turning off Cellular data, but that doesn't fix the problem. Is anyone else having this problem?

I've also tried restoring the phone as a new phone, which did not take care of the problem.

Doesn't fix it

TSX said:

Do a hard reset.

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I've done several hard resets. It will temporarily fix the problem just like toggling Airplane mode will, but the problem persists if I lose network again. This is very frustrating.

dasx said:

This?

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This is pretty much exactly the problem that I'm having. I'll start following this thread. Thanks