Identity fraud ATT

We’ve had ATT email, phone and Direct TV through ATT for years. We are always current on our accounts. When trying to add a new device to our account we discovered that someone opened another ATT email account in our names last year. They are trying to charge us $1500 for not returning the equipment when the service was cut off. We’ve been attempting to contact the identity theft fraud unit for 3 days and have sat on hold for hours and cannot get through. I want to know what address the technician hooked this service up at. Did they even attempt to verify identity through a photo I’d when dropping off $1500 worth of equipment? We’re they not alerted at the potential fraud by noticing we already had long-standing accounts at our home address??? I have their on hold music playing in my house all day because nobody is apparently there to pick up a phone. I seriously want to file suit against them for this unnecessary 3 day hassle because of their negligent acts in not verifying identity. Basically for the time we’ve spent sitting on hold for 3 days. While on hold, we contacted customer service back who said nothing they can do until we reach the fraud unit. I’m at a loss as to how to get the fraud unit to pick up a phone??