Charge for inactivated lines(they assured there would be no charges.)

I inquired with them about whether they would impose charges for inactive lines when I switched to Xfinity, and they assured me that there would be no charges. However, I ended up being billed for three inactive lines for a duration of two months. Over the course of 2 months, I requested on four separate occasions for them to delete these lines. They only complied with my request on the fourth attempt(it's been 2 months later) and informed me that they were unable to provide a refund for the unused lines