Unauthorized line

Hello. Could anyone point me in the right direction? I just noticed an unauthorized line on my account that was added on November 24, 23 in store. The line is just sitting there, with no phone and it's been charging me $190.00 every month. I noticed my bill was high but I just figured it was fees as I've been setting up payment arrangements. I went into a store and they noticed a store from out of state added the line. I'm trying to get help but the people I'm currently on the phone with are not trying to credit my account. It doesn't make sense.