You need to contact T-Mobile to find out if there is any issue for which to be rectified especially if in case it is the phone and not the network if everyone else is phones work fine in the same area. You have to go with the carrier that has the coverage you need suffice to say Verizon does not carry uninterrupted service everywhere as no carrier has 100% coverage everywhere.
Millville? That brings back memories. I was originally from Bloomsburg. You are correct there is little to no coverage with T-Mobile there.