Why are you charging me incorrectly and failing to explain yourself?

Some of my debit orders had to go off on my account and I did not have enough funds on my cheque account as I had moved funds to my savings. When I received notifications that 2 of my debit orders tried to debit and my account was now on a negative. I assumed the bank had paid the debit orders and I transferred enough funds from my savings to my cheque account to cover the negative on my account. Few days later I get a notification that I did not pay my cellphone contract's monthly premium. I ignored it because I knew the funds were deducted by my bank from my account. I get a notification again from the cellphone company yesterday to say I owe them. I then enquire with them and they send me a statement. I go into the secure chat on my FNB App and I chat to an agent named Asanda. She informs me the transaction was done incorrectly by FNB and that it needs to be reversed and I will get a refund. Shocked!! Why would you deduct funds incorrectly from my account and wait for me to ask you for FNB to correct it. Then I probe my statement and I see there was 5 of these #item no funds transactions on my account at that time. Asanda then gives me explanations on two of these other transactions, explanation which does not make sense. When I ask her more questions on it, she's gone. Then I get a Lindokuhle who gives me an explanation which also does not make sense and she also lives the chat. Third person to enter the chat is Twanano. Who tells me the other #items no fund transactions are from when I purchase something at a shop and the reserved funds remain in the balance and it does not reduce. The items no funds occurs when there is not enough funds in my balance. If I do not have enough funds in my account and I go into a Spar or pick n pay my card will decline will it not? So this explanation does not make sense for me. I then ask more questions and he also exits the chat. Is this the kind of service you provide your clients with?