Hello again, Steven, and thank you for the additional information.
At this point, they have failed to deliver you the vehicle you originally intended to purchase, so they are technically in breach of the contract you entered into with them. In addition, the fact they are attempting to increase the price of the vehicle you intended to purchase, provides you with a good basis to terminate the contract altogether and return the vehicle they did deliver. You would not typically be compelled to agree to a higher price, the law would normally view this as an "offer" but you are not required to accept it and can say no.
Since they have not delivered the vehicle you intended to purchase and because they are now attempting to charge you more than you originally agreed for the vehicle you did intend to purchase, you would typically have the right to terminate the agreement you did signed because they have breached it and reject their "offer" to purchase the vehicle you did intend to buy.
If they will not resolve this matter with you to your satisfaction, you may wish to file a complaint with a BBB or even retain a local attorney to communicate a demand to them.
I hope this helps clarify the situation for you. Please remember to rate my service once you have all the information you need. If you have any other questions, please ask me – I’ll be happy to respond. Thank you!