taken to credit bureau by MTN while i don't have contract with MTN

Three months back, MTN deduct money for contract which I never had with MTN, I makes calls regarding this issues three month back with a positive responds of being told that it was ***** and things are sorted. Am surprised currently when I go to the bank to get some money for my business, surprisingly told that am blacklisted by MTN for the contract I didn’t pay. Am currently stuck with my business because of this *********** of MTN contract and legal nonsense. I have made calls since last week no feedback and this issues is not yet resolved.