Uber South Africa sneakily change fare next day and updates debit

This happened on numerous occasions but the last was yesterday where the trip usually costs ~R50.00 however the driver changed the fare to R67. I have to dispute the fare each time and they amend it to the original fare but this time they saying I have exceeded the times this is updated. This driver told me he lives close to my drop off point so why did it change as the trip was same as before but trip is almost R20 more after he changed the amount.