Iam not happy about this

I do have a challenge with mtn store they keep on calling me that I own them I must come pay the account. The thing is I don't have mtn Sim card and I don't use the network of mtn but they said I took Sim data I get data every month wich is no true when I go to the nearest mtn to sick for help they said they can not help me because the matter is under law I even open case about this matter can hellopeter help me I thank you sm sereo