We had booked and prepaid a minivan but the lady in the counter tried to sell us a $200 upgrade - to a "different kind" of minivan! We didn't buy it, fortunately. When we came down to pick up the car, we got exactly the model that the lady at counter tried to charge us extra for.
Some companies press up-selling so hard that the staff is perfectly willing to cheat customers and try to rip them of in an attempt to meet daily up-sell quota. Incredibly irritating!!