Wesbank - Cannot keep to what they offer

Paid funds into my vehicle account in error (on my banking app) and I could not reverse the payment. I contacted Wesbank on 7 August to request a refund, on 8 August, Wesbank rep**** that they could not refund (they are not a commercial bank). They however offered to use my additional payment as a partial payment on my next debit order, and requested that I settle the difference manually. They requested my permission to proceed with the once off manual debit, and I sent my agreement for this arrangement by return email on the same day. I heard nothing back, so I requested a confirmation on 14 August, to date, no reply. My confirmation request was blatantly ignored. Wesbank took a full installment from my account at month end, so why offer to make an arrangement with me when you cannot keep to what you offer. Wesbank, wake up! I have two accounts with you, and if you ignore customers like me, my next vehicle will definitley be financed elsewhere. It is a pity I cannot rate you zero stars.