Scams only work if you allow yourself to get scammed.
Dealer calls, says they have a car in stock, but it doesn't have what you ordered, but they can install it for more money.
You tell dealer that you will come down to look at the car before you decide.
If the car doesn't have everything you want, you can tell them you'll continue to wait, or tell them you'll take it - MINUS the cost of the options you had ordered in your pre-negotiated price.
If the car does have everything on it that you ordered, then you caught the dealer in a lie, and it's up to you to decide if you want to deal with a dishonest dealer.