Unexplained toll charge on Uber fare

Last Saturday evening, I took an Uber ride from the airport to Simei under the "Pool" scheme. I was quoted $6.80 for the fare.

A few hours after the trip was completed and the fare was charged to my credit card, I received an e-mail that an additional $1.50 was charged to my credit card due to toll charges.

The driver never mentioned anything about toll charges. And there is no Electronic Road Pricing gantry from the airport to Simei.

Is it right for Uber to incur additional charges without consultation with the rider or cardholder after the ride?

Lim Choon Yong