I originally booked a fully prepaid car, but on the day of pickup, I was told it was unavailable. To avoid delaying my trip, I had to upgrade the model. However, I later found out that the cost of the originally booked car was not refunded, resulting in double charges. I have kept the payment receipt and transaction records, but have yet to receive a resolution. I don't know if it's due to internal mismanagement of the rental company or inefficiency of the platform!