Be assured that there are trustworthy companies out there that will follow through with your car transport service at the price you signed for and in the allotted time frame.
These companies may have to bite the bullet on profit, but they are committed to customer service and they want your business again in the future. For those who are stuck with the other auto transport service, you can pursue legal action. This is not how the auto transport does business and you should be compensated.
If you see that gas prices are jumping all over the board, ask the auto transporting service what their policy is in this situation before you book the service. Some of the honest auto transport companies will hold tight to their agreed price, while others may try to slip it in the contract after signing. Of course, there may be legitimate delays caused by weather conditions or traffic, but you should be able to track your car on the auto carrier from the companies online tracking to know first hand if there is a problem.