Fraudulent Mobile account added to my Xfinity account

Hello,

I recently changed my Xfinity account at a store location. I was provided with a new modem and was told that I would be placed on a new plan that would actually cost less than my original plan. I was also told about a promotion for new mobile customers. I was pleased with my current mobile carrier and chose NOT to sign up for the promotion. Later that evening while attempting to setu my new modem I was told that a mobile line was opened under my account. I returned to the store the following week to request that they remove the line from my account. It was falsely added, however they claimed it had to be investigated. I asked them to check the cameras in the store from earlier in the week, but I was rebuffed and told that they could not do that, but that it must be handled by an investigation department. 

I have stopped by the store twice and contacted the manager by text, for a total of 3 attempts at having this line removed from my account. The manager continues to not address my concerns. How can I have this line removed from my account? It has been over a month and the store location continues to claim its "still under investigation". Frankly, I am tired of reaching out to them. Can someone from a corporate office help in addressing this matter?