Free kilometers?

Hired a car via FNB ebucks. Paid for it via FNB ebucks. When I returned the car i received an invoice to pay a further amount. When I called Avis customer care they said that the amount was for petrol but when I received the car I was told i receive 200kms free per day which i did not go over. Sad to say that it feels like a *******. Be careful and read the fine print.