Nedbank personal loan

Just want to share what happened to me at Ned bank of wich make no sense to me,nedbank customers just be carefull,I've open a personal loan at Nedbank last year June,we had an agreement they they will debit every 25th of the month in my cheque account of wich that was happening every month as an agreement,now in May it happened that my pay date change from the 25th to 31st pl,I've made an arrangements still with nedbank and I've been told that was already to late for them to change the date so what is going to happen is they will deduct twice in June, thats was fine to me so in monthend June got payed monthend than nedbank deducted their money on the28th but only deducted once not twice,yesterday saw a massage saying that I've made payment of R332.51 on my savings account not the cheque account,was so shock coz I know I didn't made any payment of that amount in my savings account,went to Nedbank branch at Tygervalley centre to ask what happen coz i know nothing of that transaction ,I've been told that apparently Nedbank did a personal loan payment of May on my behalf,my question is who gave them a permission to deduct money on my savings account with out consulting me coz there is still enough money on my cheque account for them to deduct my outstanding balance in my personal loan,I called them coz need some explanations no one helped me instead they transferred me in 5 people,I was on the phone for 2hrs no one explained what happened coz want to know who gave them access in my savings account coz this is very scary to me feels like a ***** as there's not even one person explaining now what happened exactly they just told me that my loan account its been settled now they going to close is,just be careful people coz if Nedbank can have access of taking money in my savings account without consulting me what next?