FNB outstanding debit card authorization

This morning I just got woken up by an app notification of 2 transactions dating from the 26th and the 27th of March. Is the bank not suppose to reserve funds for eft payments which would then give you your balance and your AVAILABLE balance as different amounts. It is so inconveniencing because now my account is on the negatives and if they would have reserved those payment funds I would've worked according to the funds available to me and not gone over to the negatives.