Poor service

On the 23Dec 2020 I booked a car online under SIXT car rental and the balance was R4 936 and they asked me to pay R1 703.86 and I paid then the following day when I got there to pay the balance, I found out that the balance is R9 134.00 then I left the car since the balance was too high and I asked for refund. Then they said I should go to a bank.