Checkers 60 60

I have ordered groceries on the checkers 60 60 app on the 17th December, they have deducted te amount twice. I have phoned them numerous times and each and every time they tells me they have reversed my funds, but I haven't received any funds as of yet. I went to the bank they told me checkers must give me a letter so that they can clear the funds in order for the bank to reverse my money, checkers tells me they can't give me such a letter. Yesterday I phoned again they asked me for my bank statement because according to them they didn't deduct but it is showing on my statement. I am really frustrated of the service I am receiving from checkers. I want my money!!!!!