Definitely price shop. Auto/Truck rental is a cutthroat business (trust me when I say I know), and a few calls to play both ends against the middle will probably pay off, if you'll spend the time. Also ask whether you are dealing with a franchise or a corporate-owned location. You'll have more options with a Corp store, since they are totally numbers driven. Also, you can appeal the pricing dilemma you have straight to Corp HQ. Get your message in to the Customer Service people at the top, and they will often override certain parameters in order to improve satisfaction.
Or not. But, it can't hurt to try.
Also, check what pricing should be when you contact HQ...I've found that U-haul agents are often totally untrustworthy, and price gouging is rampant around here...try over $1.00 per mile!! On top of the daily rental fee. No shiatsu, boys...
Luck!