Service seemingly transferred to an account that's not mine

Hello,

What started off as a minor billing issue became a very different issue over a long 1 hour, 15 minute phone call where I was transferred to different departments over 6 times. I have no choice but to believe, based on the information I know, that my mobile service was transferred, unbeknownst to me, to a different account owned by someone with the same name as me that I have no connection to. I do not know their phone number, their email address, or their physical address. I was hung up on after an hour and 15 minutes on the phone, with nobody able to help me. I need to talk to someone ASAP to resolve this, as it's completely unacceptable and seemingly a huge security breach.