MTN billing me for a non-existent contract

MTN has been billing for a contract I don't have and now they have sent my details to their legal department for collection. They called me saying I owe them for a contract with my Telkom mobile simcard. after long dispute, they advised me to send affidavits that i never took contract with them and I am not receiving any data/free minutes from them, which I did, But still today I am being threatened with court action for a contract I never took, a cellphone that I never had and they claimed it was sent to me and I am still receiving data from them. Please help as my please with MTN has fallen on deaf ears.