What you agreed should be on the initial paperwork.
Take the car and leave it at the garage and tell them it’s not what you ordered.
It happened with us once and the dealer said motability are happy to accept the car they gave me even though it wasn’t the car we ordered. I told them I would leave the car with them as it was no use to me. Five minutes later the manager came out and said they had re-ordered my car and to use the one the gave us until the new one arrived. It was only six weeks delivery at that time so not sure I would do the same if I had to wait nine months.