FNB does not allow disputing of debit orders

I have been trying for two weeks to reject a debit order on my account. I've been told to do it online or via the app to no avail. Apparently neither my app or online banking device are verified. No one can tell me how to do this. The branch tells me to phone the call Centre, as I cannot reject a debit order via the app or online banking over a certain amount. I phone the call Centre who tells me debit order disputes are unavailable. Does anyone at FNB actually know what is going on with any of their products!