contract not cancel till today-***

good day kindly note i called mtn today my ref-from mtn is *** i was advised that mondo did not credit nor cancel the contract i need this canceled with immediate effect because i did return the item in store within 7 working days as requested i received a bill which i have attached if my account is debited this month i will sue mtn and mondo for negligence, i have attached a copy i expect a response before close of business today or else i will write to hello peter and expose your company incompetence that is costing me time and money. i received an sms from mtn telling me i will be black listed i am not happy i need this sorted out