Dallor Rent a Car review: Charging service fee to cancel

I Booked and reserved a rental car for 6 days. Then I realize I needed to reserve a full-size vehicle. I now had to cancel the existing reservation and book a new reservation with the vehicle that work best for me. The Co. refunded all except a service fee of $50. This is not good business at all! I have called the company with difficulty, there site indicates to try again after filling out all that applies. I spent 4 hours working to get an answer or to talk with a representative. I went online both, Expedia & Dallor rent a car, trying to resolve this issue. The representative suggested I call the rental. My Bank account has the agency (Expedia) who billed me for the amount, less $50. While asking why is it less $50, the rep. said it was the rental policy. The dates I reserved for the rental is stated below:

Date reserved: July 21, 2023

Date Cancelled: July 25, 2023

Rebooked at the same co. July 25, 2023

Booking date reserved: Aug. 18-24, 2023