Going in the red caise the bank makes a mistake

Well today I get message from AB stating they blocked my account I go into the app to check just to see they took money and put me in the red. Go to the bank and get stated that the banks made a mistake but you need to pay it. How is this fair to the client to state that I as a client that got no feedback no communication no nothing from AB AND I HAVE TO BE PUT IN THE RED cause the bank made a mistake. This isn't right this is not on you make a mistake you own up to it you don't blame the client nor do you state I have to pay for stuff more and more I go in the red cause they think it's fine