Dealer Change The Deal Days After You Already Took It Home?

[KJS]

Got a call this morning from the Dealership about some story that there was an error in the numbers they came across when "completing the final processing". That they are going to try and work through it, but there is a possibility that the payment might have to be changed if they can not work through it? What kind of bull**** is that? Is that even legal? We signed everything and took the truck two days ago, is it not a done deal at that point?