No, you're not being unreasonable.

I had a similar experience at PHX. My car was in the shop and I needed to drive to SoCal, so I reserved an "intermediate SUV" which Budget described as a Ford Escape or similar. This was on sale, as it were, and was only a few dollars higher than renting the full-sized car, so I figured why not.

Got to the counter and Budget counter and the agent looked at my reservation and said she, "Oh, good, I have a very nice Buick SUV for you." She ran my credit card and entered my DL and the amount popped up on the screen in front of me and I was told to initial the areas and sign.

I looked at the total and it was $100 more than my reservation. I told the agent there was something wrong and pulled out the printed copy of my reservation. She looked me directly in the eyes and said, "Oh, I upgraded you and that is the cost of the upgrade."

I told her I didn't request the upgrade and to put me back in the original car. She said, "But that means I will have to cancel this transaction!" I shot right back, "Them cancel the transaction and give me the car on my reservation."

Of course, the CS aspect went downhill from there and she begrudgingly gave me a Dodge Nitro at the same amount as my reservation.

I filed a complaint and demanded to speak with the district manager, but never got anything more than a form letter apology and a $25 voucher.

And I am willing to wage a week's pay that the same agent at Budget PHX is still doing the same slight-of-hand maneuver to any customer she can.