How do you register the phone to the T-mobile network? I did a master reset and still no network. My phone only offers me ATT network as a choice.
Do you have a T-Mobile sims card in the phone? Try taking it out and reseating it again. If that doesn't work you may have to get a new sims card.
Did you try luvduchovny's suggestion? If you have access to another T-Mobile phone, try your SIM card in the phone and see if the same thing happens. If it does, that shows your SIM card needs to be replaced. Let us know what happens!
Another possibility will depend on where this is happening. It is possible that the area you are in does not have TM service - either permanently or because of a temporary signaling problem.
You didn't say whether you were able to connect to the AT&T network? If so, then you are most likely in a roaming area and will probably not get direct TM coverage any time soon.
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