Get it in writing. Any negotiations when buying any product need to be recorded in written form. If you do not have a copy in writing then you can consider whatever has been discussed as non-binding. Do not take anyone at their word. They may have believed what they were telling you at the time, but given time to cool off, they may re-assess. If a dealer is offended you asked for a copy, it could mean they are being less than 100% truthful. That’s why you need things in writing. If nothing else, it acts as a reminder to both parties. The worst business meetings are those where no proper notes are taken, so everything has to be discussed again at the next meeting.