Poor service

I bought a meal on Saturday and it cost R162. When I collected my food I paid R200 CASH to the driver and said he can keep the change. Uber came back to me today saying I need to settle my R162 bill which I paid for in cash. After emailing them they cane back to tell me they writing off the R162 as a service gesture. I DON'T NEED YOUR GESTURE. I need my payment I made to reflect as paid not as you writing off arrears.