Service trip charges are standard for most industries where a technician needs to come to your house. The parts and labor are usually all that a warranty covers. If the dealer you bought your car from had to send a technician to your house, you can bet there would be a charge. Instead, they make you bring the car to them. I have a home warranty. My garbage disposal failed. They came out and fixed it with no parts or labor charge, but I had to pay them a $90 trip charge.
I know you are frustrated but this is standard practice. It costs a lot of money to have a vehicle, tools, insurance, wear and tear on said vehicle, and to pay a factory trained technician a living wage while he drives around in traffic to get to your house. Warranties do not pay for all of those things. They cover the parts and the labor.
If you provide more information someone here may be able to better assist you and possibly diagnose the issue.
