Follow through with the disputes. Send the CA a letter with your dispute. I had a similar issue with an ATT mobile account years ago. Keep your paperwork if your situation ends up anything like mine it will rear it's head again.
Don't just rely on the Experian dispute to clear it up. TGhey will validate the debt with the bill of sale information from T-Mobile or who ever they bought it from. In your letter to the CA give details the one thing I had on my side is that that phones purchased and addresses used were in Florida. I live in Texas. After about a week after sending the letter call them talk with their CRD (dispute) department. And when they ultimately remove the account demand a letter from them. That ATT account popped up 3 times on me and I have an Miami address on my CBR that never was removed.
And file a Police report you can get a head start by filing an ID Theft affidavit at the FTC website. (https://www.identitytheft.gov/) Include copies in the letter to the CA. And keep an eye on your credit reports.
