INCORRECT BILLING ON ACCOUNT

I have an account with Mr Price , i received a call early October from one of their consultants , who told me that they are offering all the accounts holders sim cards which will be loaded with airtime . The consultant assured me this will not be charged on my accounts its free , i can throw away the sim-card once the airtime is depleted or I can call in and port if i want to . I have just checked my statements and they are basically charging me since October . This is very annoying and i am so ****ed off , if this does not get sorted immediately i will close the account.