Originally Posted by jackal

Sometimes, a rental car agency will be in an oversale situation (just like airlines and hotels, who also typically slightly overbook due to a relatively consistent no-show factor).

Ultimately, though, as long as you fulfill your end of the agreement (meet all rental qualifications and show up on-time for your reservation [within 2 hours of scheduled pick-up]), it is Dollar's responsibility to accommodate you. If they do not have your reserved car, they should offer you a better car at no additional cost to you. If they do not have anything better to offer, they should make arrangements for a comparable car at another company at no additional cost to you. If no one else has a comparable or better car, Dollar should either offer you a smaller vehicle with appropriate compensation or make other arrangements for your transportation at no cost, minimal hassle, and appropriate compensation to you. That usually takes the form of transporting you to your hotel at their expense and offering to bring the car to you when possible, but I know some managers who have been pretty creative with their solutions to this problem.

You may need to hold their feet to the fire a little bit (be polite but firm) to get what you fairly deserve, but it is ultimately their responsibility to fulfill their obligation to you. Do not let them just tell you, "Sorry, we can't help you."