Was billed for a Blackberry Z - case nr ***7

In June 2015 a Blackberry Z was billed on my account. After numerous phone calls i received a case number ***7. I have been told to forward an affidavit which i did on 05 November 2015 and this morning when i called their (customer service) told me that there is a case number and it is still under investigation. This investigation is not my problem....i need them to take it off my billing account and refund me!!!