Other Car Rental Programs/Partners (ie. Alamo, Enterprise, Sixt) - Enterprise: Merging reservations

I wanted to book December 26th through January 5th at a neighborhood location outside PIT. After trying all my usual discounts in different ways, I realized I could save some money by booking two reservations. In all it's about $244 for the whole trip and that's a pretty good deal for 10 days, I think (rentals out of PIT itself are never as cheap as other cities for whatever reason).

I'm going to be out there and renting from the same place in two weeks. I'm planning to ask them then if they can merge that, but will that even be possible? Can those people even view those reservations? If they can't merge them, I wonder if it's possible if they'd just book me a new rental under my total for both so I don't have to bring the car back. Has anyone gotten away with anything like this? It seems so dumb because this place is in the sticks and I've actually gotten the same car my last 2 or 3 trips out there so I know what they'll give me.

And if anyone thinks they can do better than $244 for 10 days out of the actual airport, please let me know because that would be more convenient.

The short answer is probably not. The long answer most likely has to do with taxes. I work for Enterprise at the Phoenix Airport and our taxes are 34%. However, if you go to the local branches the taxes are more like 16%. Unfortunately, we can't do anything about the taxes so merging and taking into account taxes is nearly impossible. Most likely though they'll be able to view both reservations as at least in Phoenix local branches and airport locations are on the same computer system.

I figured that was probably the answer. It's not a huge deal to drive there to renew the reservation, but I'm sure I can't be the first person to try this. I wonder if they would be willing to cancel both and create me a new one for the whole trip for that price.