Mobile and West Mobile are covered with T-Mobile's own network, however there may still be areas that are outside their planned service area.

You should put a help ticket in at: http://support.t-mobile.com/caseSubmitForm.html

They are VERY good about looking these up and letting you know if coverage is marginal and planned to be improved or if it's not a known issue (or a cell site problem).

Give them the FULL address of the location, they will use this on their GIS cell site lookup and they can rough rate the quality of the coverage on that address.

Put it under, Coverage, Coverage Problems.