Can't change my address on my account?

I set up an online account for my pay-as-you-go phone. It required me to add my name and email so I did. I didn't want to put my address on it for privacy reasons. Everything seemed fine, address being blank. I checked in sometime later and found that my address said I lived somewhere in Preston, TX. What?! I tried to take that off there and delete it, seemed like it worked. I check again another day and that address is back on there?! I tried to change it but an error kept popping up saying they're having problems with their system. So idk what's up with that. Maybe whoever previously owned the number lived there or that's some default address? IDK. I changed the password because they required a stronger one, so I did. I wouldn't think it would be something related to being hacked but it's weird. Any input?