Failing to keep track of payments

i am in arrears with my payments. I am not denying this. But i have made arrangements to pay every month. I paid my April installment at a Checkers as Game themselves advised me to. Then, days later, i get an email from a law firm saying I never honored my arrangement and then see an attempt to deduct the FULL BALANCE OF R 24 000 from my account!? This is wreaking havoc on my credit score. I know I'm originally at fault but these arrangements after the fact are precisely to avoid these situations.

Unacceptable.