Why can't I reverse debit orders from Business Account??

This afternoon, I was at FNB fordsburg Branch to do a reversal of a debit orders which I had it stopped six months ago, which keeps popping in every month but it's refused me to reverse them, after having spoken to one of the people working at FNB in fordsburg to assist still we couldn't manage....

I was then told to try and do it via covid 19 app, which also didn't give me the options, I tried calling FNB business contact, their line kept dropping my calls on several occasions....

The debit orders are from multiflex one for R349 which was done on the 30th of April and the other one R398 which was debited on the 31 st of March 2020 both of them needs to be reversed asap and block these people from gaining access into my business account....