I tried to use the Uber pre-ordering for a taxi to the airport a couple of weeks ago. Magically a surge started in my area a couple of minutes before the order

I tried to use the Uber pre-ordering for a taxi to the airport a couple of weeks ago. Magically a surge started in my area a couple of minutes before the order was executed. After a driver had been routed, they notified me there was a surge, but did not tell me the amount. It wasn't until the ride finished that my estimated $30 trip actually cost me $85.