How can someone have my cell phone number deactivated and activate one?

[AC Question]

Received mm2 message on my phone and called AT&T. They said someone used last four numbers of my SSN to activate a phone on my account

 

[Rukbat]

Re: how can someone have my cell phone number deactivated and activate one?

Go to an AT&T store with a picture ID (like a driver's license) and tell them that you didn't authorize the activation, that it's fraud, and that they can go after the individual who did it for payment. Then go to the police and make a criminal complaint for fraud and larceny against the individual.