How does one reach a callcentre consultant at MTN?

I had one huge whack debited off my current account with a reference starting with MTN. The issue is that I'm not even an MTN subscriber. I have been into a local MTN store and given their head office number which doesn't get answered, looked on the internet, dialled 1023 and each time the numbers leads to a dead end. I have had the amount reversed back into my bank account (as unpaid magtape) and was told by my bank that the onus is on me to get hold of MTN to make sure that this doesn't happen again as they somehow have my banking details. This would seem relatively simple to do...one would think but all numbers lead to NOWHERE!! Please can someone give me a number to call?