wont reimburse

I have R725 owing to me and they won't pay up. They have asked me for a bank statement, copy of I.D. and proof of payments. I can not show proof of payments because it was done at spar or Checkers last year (cash) and did not keep the receipts. Now I can't get my money back because of that. On their system, it shows that I have credit but can't get it. That is not right.