Incorrect Debit

On the 17 July 2015 i went in the store to purchase items to value of R498 . I paid with my card, but the speedpoint did not generate a sucessful or failure message, and I was told it was not working and should go to withdraw, so I did and paid cash for these items. On monday i get in contact my account has been debited by earthchild, when i went to the store with proof, i was promised investigation into this. Its over a month now, i want my money. I have proof on my bank statement as well. Someone get back to me ASAP.