Unhappy with the service at capitec bank

I have two loan accounts with capitec bank and I signed a contract that says they should debit from my fnb account. I had some funds on my capitec saving account as well. For years the debting has been like that until May 2020, capitec debit from my capitec savings and not from FNB WITHOUT MY CONSENT. June 2020 same thing but this time around the no suffient amount to debit both loans from my savings, so bounced. Now capitec has the nerve to send me a message saying my account is in arrears.

As a good citizen and customer I called them to find out what happened, a consultant told me that it was the bank system that changed my debit account from fnb to capitec without my consent. When asked why she said she doesn't know why the system does that but am not the only one. She changed my details back to fnb and she read a long T&C and I wondered if that is the case why is it so easy for the bank to just change their clients profile without consent. The consultant referred me to complaints management since I couldn't agree to their term on paying for the arrears that was not my making in the first place.

I sent an email to complaints who asked me for my fnb bank statements to investigate, later complaints said they sent me an sms indicating the change of debit account and I told her yes I saw the sms and I didn't not respond since my salary is not paid at capitec but fnb so it didn't make sense because it would have meant every month I must transfer money to my capitec saving account for the debit to go through. When I told her that she said she will investigate further. Now the investigation response says there is an agreement in my contract that says if my primary debit account has no money the bank can debit from my savings. I said to her show me evidence that you didn't get the money from my fnb account on the day you suppose to debit... No evidence because if there was my fnb bank would also flag it. I feel capitec doesn't want to take responsibility and accept that their system is causing problems for clients. When I reasoned with the complaints lady... She referred me to banking ombuds to lay a complaint against the bank. I felt insulted, it's like they don't expect people to use their common sense or brains to process what they are telling them.

Because of frastration I had to find money somewhere and settled the account in arrears, unfortunately I didn't have enough to settle both accounts, SO AM STILL STUCK WITH THIS BANK.