Absa bad service

I am very upset with Absa,I have been a client of theirs for roughly 30 years. Every month on the 25th a payment goes from my wife's FNB a/c to my Absa a/c to cover our debit orders.On December 25th my wife's payment went through,I have the proof on her cellphone.Yet on Monday the 28th December when our debit orders went through some of them were returned due to insuffient funds.I am of the opinion that this is a failing on Absa's part,in making my name bad with my accounts and I feel that they must pay these finance charges.I sent them an email on 31/12 requesting an explanation,all I received back from them was "your case has been closed".I then sent them a follow up on 31/12 quoting their motto on their emails is "at ABSA ,we are committed to giving you exceptional service" and how is this closed when no one has contacted me.A week later I received a reply stating once again"Your case has been closed".How can a bank treat their customers like this?