OVER CHARGED FOR A TRIP

Yesterday I was running very laye to wprk, taxi's were very slow. I requested a uber ride from Jozi to work it cost R51. When I arrived at my destination, the driver says I owe R108 shockingly. I asked how it got there as my ride says R51 he said maybe I owe uber there is a trip i did not pay previously. Since when does uber allow rides credit? I paid the driver as I was late and I thought I will sort this out with uber and ask them to credit my account for the overcharge but they are not reaponding and O am so dissapointed and do not think I will ever use their services.