Upset about unauthorised withdrawals

Good day.. I have a huge problem. Every month fnb homeloan deduct from my savings money.. Even if my debit order is successfully on the 27th.i have informed you on numerous times that u cannot do it without my permission and what if something happens and it is an emergency are you still going to tell me I must wait for my money for 5 or 7 days u til funds are clear. I have never missed my debit order so on what grounds do u keep taking from my savings. I would understand if I skipped my debit order then u have every right to withdraw from my savings.. Now you deduct double every month.