Uber change prices after the trip

I will never make use of Uber again😡 I booked an Uber ride last night, paid the trip R53, this morning Uber attempted to deduct another R27 from my account. How can the trip payment change afterwards? They have the trip details and distant to my destination. Why change the total after the trip when my destination stayed the same. By the way I wouldn't have used that trip if I had been charged R75 for the trip.