Uber Eats are a bunch of *****s

I had a voucher of R100 for Uber Eats, i ordered a meal of R75 and with their charges the final amount was R99. This my voucher cover for this. The App stated i must pay the driver the R99 in cash which i dont have so i had to cancel. They still billed me for it now i have a fine on my name. Uber Eats are now trying to deduct the amount from my bank account. Why? My bank Acc is in arrears so everytime they try to deduct i get penalised on my Bank Account. They are ***** why should i pay cash when my voucher covered for eveything? DONT USE UBER EATS.!!!!!