Totally ****** Unacceptable

I recently took out a data contract with MTN and not only did they take 4 months to activate the ****** simcard but they over debited my account with almost R400 now when I went to check the balance outstanding on my account it said that I owe them over R700 for the month of June and July after only agreeing on a R199 contract. This is unacceptable from MTN and it cannot be accepted. I need clarity on this situation otherwise the debit will be reversed right after it gets taken off my account that I can assure you.