Cell phone service is ever-expanding. Carriers are endlessly adding new towers and transmitters to improve and widen their coverage areas, even in remote areas. Sometimes cell phones do not recognize these new provisions and need to be prompted to do so. Some service providers offer the "*228" function, but T-Mobile does not. There are only a couple known ways to improve the service signal with a T-Mobile phone and enable it to recognize the most up-to-date coverage.
Power down the T-Mobile handset. This can be done by pressing and holding the power button, or removing the battery and putting it back into the handset. Now, power the handset back up.
Wait for the phone to fully boot up. The phone has now been forced to re-register with the network, thus ensuring that it is using the strongest, most current signal available in the area. This is the easiest way to ensure the highest-quality signal to the telephone.
Buy a cell signal repeater. If the signal does not improve from the power-down method, the only other option is to purchase a cell phone repeater, which takes the strongest signal it can find and boosts it within a small area, such as a house, car or building. These devices start as low as $200 and can cost more than $600.