Standard bank vehicle finance nightmare

I had a vehicle fincanced through standard bank and it was written off, my insurance paid the balance and I had a shortfall.. I have been paying the shortfall through debit order and every month after the debit order, I get emails from standard bank saying my account is in errears and I will be handed over, I have been sending them my proof of payment and also calling their collections department and none of their contact agents help, they keep saying they will get back to and they never do... Standard bank has been a nightmare the whole of 2019 and I have told them multiples times I will sue for harrasment because I can't be paying my account and sending proof of payments then told I am in errears.