Why am I struggling to change my banking details

I have been trying to change my banking details since August last year. I have submitted proof of residence, front and back copy of my ID, a picture of me with my ID (previously also a note indicating the date and the case number, but that is too much work to keep doing), stamped letter from my bank, 3 months statements. I have done this regularly since August, but nothing happens. I keep being told to submit documents. I have called and discussed with call centre operators, and I still seem to be doing something wrong but no-one can tell me what I have omitted. I live far from the nearest SARS offices. I changed my bank because they closed their branch in my town, and have not had trouble changing my banking details with the financial company running my RA, my company who pays me every month and everyone else who I have debit orders with. What exactly makes it so hard for SARS to just change my banking details?