Salesmen always tell you that but legally you are not on the hook until you actually take delivery of the vehicle. So if the Jeep you're after is not exactly what you want to take home for whatever reason you can refuse to take delivery. And even though you have signed a contract they cannot force you to drive the car off the lot.
Now, if you just changed your mind without any other cause they may try to cause trouble for you and hassle you by saying you were not dealing with them in good faith. Otherwise, if you have a legitimate reason why you do not want to take delivery of the vehicle you are in the clear because the dealership did not uphold their side of the implied contract.
If, on the other hand, you are not exactly sure and want to actually lay eyes on the actual vehicle you want and test drive it rather than committing based solely on the window sticker you still should be able to do that. If the salesman won't budge go to the manager than to the dealership owner if necessary. If they can't/won't see the logic in trading a vehicle on their lot that no one is interested in for one that is a probable sale then they're not the kind of dealership you want maintaining your new car warranty anyway and you should approach another dealer. Threaten to do this and see how they change their tune.
Twice in my life I was pressured to sign a contract the day before the vehicle was ready and both times (on advice of attorney) ended up not taking delivery. Even though the salesmen were really ticked off and threatened "legal action" they were totally empty threats and the whole thing was dropped when I told them I was writing a letter to the owner.
Don't let them bully you. Salesman don't see past their commission. Good luck!