BS”D
1) Overcharging and using roundabout routes. Happened to me when I used a non-Jewish car service for Purim deliveries. Agreed to one price, he charged me another. Also happened to me with a Jewish service when I relocated a few years ago and needed to get to the airport. The first one agreed to one price and then said he could not make it. Second one charged me more.
2) Unsafe cars and drivers.
3) The unthinkable.
Use only a known, community run car service or a regulated cab.