Yes they should have the right this just happened to me months ago. I went to the comic book store and offered my pokemon cards for $100 and the offer was rejected, so I had the right to make another offer before the whole offer was terminated and I offered $20 for my cards and I got the deal so this real life example of mine should be your answer and help you out brainly user, and be aware of who u are being offered from because that person offering u could scam u for your money and cheat u out so just be careful and yes for the whole question u should have the right to negotiate before the offer is considered terminated.
