Refuse to give my money

I made a instant money cash send infront of the till as I forgot my card and wanted to pay my groceries. The cashier called the controller to authorize he then incorrectly pressed something redeemed my voucher and I have not received my R2000. They told me to come back the next day. I have proof from my bank that my money was withdrawn at their shoprite and what time it was withdrawn. They keep telling me it does not show on their system but I have proof and witnesses. It has been 4 days They still did not give me my R2000 and keep telling me about head office.

Please help