Refund on duplicate transaction

I made a purchase in store when the systems went offline, the teller informed me that the transaction was declined and we do the transaction again. The second time it went through. Two days later i received another notification that the same amount was deducted from my bank debit card. After numerous calls being put on hold, cut off or being transfer to wrong ext i went in store with a bank statement reflecting the two amounts that went off a well as the slips. I was contacted a few days later and was asked for my bank card number as a refund will be made. No refund was made to date. I contacted head office and they assured me the store manager will contact me and sort it out. The store manager did not contact me but one of the assistants in the customer service department called telling me that the money was not deducted twice. When i explained to her that my bank confirmed it went off twice as they have two merchant numbers for the transactions she kept on saying that it didn't. I have an account with Edgars and i honestly do not wish to pay them until this matter has been resolved. If they do not want to give me a refund i will gladly have them deduct that money from my account