Overpayment

This is not directed to the faults department my story is I went to Sizakala in Megacity sent my mom to pay only R1000 for electricity the cashier charged my card R3000 I don't know how we went from 1000 to 3000 mom complained they said there is nothing they can do about the charges called capitec bank they also said they can't do anything mind you I have to buy groceries my salary doesn't cover all our expenses in a month called customer care service they dropped the call on me. I'm I don't know what to do in this situation the Sizakala employee told us they can't reverse the money