NOT EVEN CLOSE The mousesavers code ended and existing reservations repriced. The
UT contract code is still active. The OP presented the necessary documentation and was given a car. Ill call it a billing error. If you disagree I'LL go with fraud. The franchise lost the ethical war when they released the car subject to the rental terms. Any fine print is likely to be interpreted in favor if the renter.
I think you have it reversed.
Budget would be on my don't rent from list if they decided to double the agreed rate after the car was returned.
Edited to add looking for trouble if he mentioned movie tickets. Car rental was booked through a TA period. No reason to discuss. I suspect the rate was intended to be sold with hotel and or air without the customer knowing the breakdown.