Went to a Hyundai dealership only to not sale used car.

I have a 2015 Toyota, valued at 3877$ via KBB. They offered 3k. That’s fine. The problem is, they offer a coupon and if used adds 1k on top of the offer. So 4k in total. They back tracked and said that my car is actually worth 2k and then 3k with the coupon. I double back and said no. You offered 3k without the knowledge of the coupon. The car should be 4k at that point. Personally I was just trying to get the most value out of my car as I wanted to do a trade in. I was looking at a Toyota rav4 hybrid which sells at my credit score with 10k down, like 32k. So he just lost a sell. Lmao

Edit, failed to add my question. Is this a common issue among dealerships? And what to do from here