MTN doesn't want my money, but wants it

I took a contract with MTN in July 2017, as an anniversary gift for my gf. I completed all relevant documents and walked out of the store with the new phone in hand - thinking my part of the admin was done. However, after a few months, whilst checking my information on Transunion , i noticed that my MTN account was labelled Handed Over (Legal). To my amazement it seems that MTN did not debit my account for any of the months since i first took it out. After signing all forms authorizing MTN to debit my account each month, i had no idea i had to be checking my bank account every month to make sure. My salary changes quite often so i did not notice this at all. Once i found this out i called the Contact Centre, and no one could help me because it was being dealt with by legal. I asked for their details to contact them but for some reason the agent could not share this with me. i asked for them to contact me, but again to no avail. I eventually went to the store and the agent checked the system and under "Payment Type" it stated "None" instead of "Debit Order". Now who's fault is that?? I paid the (large) outstanding amount. This month i actually checked to see if they debited my account. But again nothing! It's absolutely ridiculous that my account gets handed over and my credit record must suffer when MTN just refuses to debit my account. Due to this i have to run to the store every month to see if there's any progress. Never, never, never again with MTN. Please be very careful with MTN, you may leave the store thinking everything is fine but with these guys it's just nonsense. To top it all off not one person from MTN has contacted me as yet.