walmart wont change my address

Not defending TMO but actually, it's Walmart's "fault" (actually their misinformed developers) for relying upon inaccurate IP-based geolocation services - these are notoriously inaccurate with mobile carrier infrastructure. There's nothing in the IP standard that says anything about location except country - those using the technique are guessing and some guesses are better than others. It's a long-standing issue for mobile because their physical network infrastructure differs dramatically from that of wire-line (land-based) services. Be thankful you're not on satellite internet - when I was on it my "local" Home Depot was some 2000+ miles away unless I used something like Location Guard for Firefox or Chrome.

Reliance upon GPS location is the solution, but not all devices offer GPS and even then apps must have permission to access it.

In the case of the Walmart app you need to allow it the precise GPS location access. You can also specify your store and it seems to remember it. If using a mobile browser you need to allow the browser access to precise GPS location. In the case of a laptop/desktop  browser you're pretty much at the mercy of the geolocation method and services a site opts to use (Location Guard may be useful when using Firefox or Chrome if the site uses the browser's API). Browser sites may also reply upon cookies once you've established your correct location. Otherwixe you typically have to login.