Magtape Unpaid

Good day I have a problem...I have a monthly debit order that goes of on my account so the end of June I made sure to leave enough money for my funeral policy and my other debit order to go of I recieved a notification that my debit order went as scheduled just for few days later for MTN to send me a message that I owe them went through my statement and saw MAGTAPE UNPAID please explain what it is cause to the research I did means that my bank reversed my debit order without my authorization meaning this affecting my credit score due to you guys using my personal stuff at your own will now I owe MTN and I have to pay the extra charges on my account,on top of that you guys take unpaid fees amount of R115 from my account for your damn mistake just to add to the pille you guys deduct my policy amount but double plus unpaid fees cause by you so ..but you dont fail to reverse your ridiculous service amounts that amounts to R500 almost especially an account that not being used. I'm very disappointed in this service from FNB further makes me want to close this account and move to another bank that looks out for their customer.