STOP CHANGING MY DEBIT ORDER DATE

I have a personal loan with Nedbank My situation started last year July... my salary is paid the last Friday of the month and it's been the same the past 11 years. July 2021 Nedbank decided to take the installment earlier which resulted in unpaid. I got a call to tell me that my debit order did not go off, after I explained and send through my contract a Manager phoned me back apologized as they loaded the wrong debit order date. My debit order as specified on my contract should go off on the 1st of every month. I told the manager they can take the payment for July but he told me due to the error on their side I will skip July and the order will just be taken 1 month extra after the full payment is paid up, which mean I will just pay an extra month. And I agreed. Since November 2021 Nedbank has been harrising me in phone calls about my "unpaid" arrears. I have spoken to so many people explaining the same story over and over again and told everyone they can go back and listen to the conversation but Nedbank keeps phoning, and I decided to block each number as I am tired of explaining. The 2nd thing, as I said the past 11 years I get paid the last Friday of the month and Nedbank keeps changing my debit order date. I received a message again tonight stating that my debit order will go off on the 22nd July wich means my debit order will not get paid as the 22nd is not the last Friday of the month. If I have a signed contract stating the 1st why do you keep changing it. I am so fed up. A contact is a binding document so STOP CHANGING MY DEBIT ORDER DATE. IS IT SO HARD, SERIOUSLY IM AM NOW REALLY GETTING TIRED OF THIS ****.