Disappointed service and dishonesty with drivers

Today taking a trip to workplace the driver had taken the wrong route and had charged extra even though trip had been on promo. The driver had resolved the issue as he understood that it had not been our fault that the wrong rout was taken and allowed us to pay the promo amount. This evening another trip had been booked home on a promo amount and when trip had ended the driver had changed the amount last minute. My complaint towards this is that after I had checked the driver about changing the amount I was told to look properly on the app. I can read and i find in unacceptable that if a promo amount is given the driver should stick to the amount that is needed to be paid. Worst scenario if we were not aware that amount is been changed . How are we held responsible to pay extra if the driver is been dishonest with payment