Reserved a car on 0% to be told the offer of 0% is not available

Reserved a car advertised as 0% finance over a period of 24 months and paid a reservation fee. I have the quote via email to show this finance example from the dealership and the deposit receipt. They called today to say that the 0% offer is not available on this vehicle despite the advertisement on the website of the vehicle (having spoken to the finance company).
What am I entitled to? I think this is very bad?