Uber driver changes price after trip

So I booked an Uber trip from Bassonia to Sandton today, I confirmed the trip based on the price quoted. Arrive in Sandton, rate the driver and add tip. Next thing I see the charge is adjusted by R75 on transaction coming through my bank app - how is this possible, it's not acceptable that the price be increased without the passenger being made aware. And no reason on the receipt. I tried getting hold of Uber to get a response but the App is so unfriendly ito options to select. Shocking!!!!!!!