********** and unauthorized MTN debit

A debit order for MTN went off from my FNB account. I have never contacted MTN for any of their services thus this was done **********ly. I tried calling their customer service which is absolutely useless since you cant speak to an agent. I emailed their ***** division who told me to contact their customer service which doesn't operate as explained. I am frustrated and need to know how to contact them so they can give me a response as to what happened and for them to remove me from their system