Unexplained Debit

Last month due to the 1st of May being a holiday my usual debit order (that I have never had any problems with for over 2 years) did not go off of my account. <br> On the 18th of May I received an sms stating that my line will be blocked due to non payment. I followed up and found the issue with my debit order and made the payment immediately however I was still stuck without a phone for 3 days. <br> <br> Two days later my account was blocked again although I had a sms stating that they had received my payment. after 4 days of unsuccessfully trying to contact the call centre I went to the local branch to get help. The lady there did help me as she showed me on the system that the payment had not been allocated. when my service came back on I received an sms stating that MTN will debit R880.40 on the 1/6/15 This is where the problem lies. I have a top up account and my monthly bill is R200 so I have no idea where MTN got this amount but it was debited and as the call centre is still on strike I have not been able to speak to anybody to help me. I feel that this is terrible service! <br> <br> Thank you