Oh no! I'm sorry this happened to you, marie1980e. I'm not exactly sure why your SSN would be different but that's something that's correctable. You can go to the closest Retail Store and bring a government issued photo I.D., proof of address and your social security card to get it updated. Again, I'm sorry for the hassle but it's definitely something we can get fixed.
With all the data breaches and info theft going on T - Mobil executives, when someone calls customer service and all of a sudden the last four digits of their social security don't match anymore (even though they matched before for years) because their social security number has been changed, THAT IS A CAUSE OF GREAT CONCERN AND TOTALLY UNACCEPTABLE ! Is your server malfunctioning, or the system has been breached by a software which jumbled up customers' information in the process ? What good all the service you provide would be IF YOU CANNOT PROTECT OUR IDENTITY ! IF THAT IS WHAT'S GOING ON.
I have just run into the same issue as marie1980e -- My SSN and all other info was good when i signed up but NOW they say it doesn't match up and i dont have access to my account - they need me go to store and bring ID's. I smell something very wrong a GOOD REASON TO CHANGE SERVICE PROVIDER - clearly Tmobile is hiding the fact of possible security breach! My lawyer will be involved on this very soon!