Very bad service - Paid off my loan 25th Nov, payment still not allocated

I paid off my loan with African bank on the 25th... as soon as I did that I called to notify them that i had paid and they should please make sure i'm not debit the installment amount at the end of the month. Well because we are taken for granted, I was debited the installment amount. I have been calling them ever since to please allocate my payment and make sure my account is settled. even today I'm yet to be cleared off. All they can say for themselves is that I paid using the "wrong method"... I paid from my Capitec acc to theirs (EFT), how is this a "wrong" method, why did they give me the account number then... This is after i struggled and failed to pay using their direct link on their internet banking. I was advised by them to pay EFT, and then they come around and say "I used the wrong method of payment". I really need the settlement letter.