Very unhappy

Tell me how can MTN debit my account R7000 and they cant tell me where it came from they cant give me a strigth answer I went up and down. Am a pensioner and I dont have this money I have always paid my account on time and have been with MTN for almost 10years. Even if the account was hacked should they not have confirmed I'd number account number of anything... all calls are recorded what happened to that calls....