No resolution to double debits

I took out home internet on 29 July of which I paid incl prorata of R510. On 4 September I was double debited and what was weird is that my invoice shows a debit for Aug, Sept and Oct! No one at MTN Parow Centre could explain why I was double debited or even debited in advance. I logged a query on 24 September and till today my money has not been refunded. It's the first time doing business with MTN but the first impression left a bad taste. They debit on time but can't refund the money! Not one phone call or sms or an attempt to resolve the matter. I was asked for a 3 month bank statement and this I sent on 21 October, but still nothing! Very bad service indeed!