Well, sadly this is exactly what mechanics (dealerships, local shops, or the guy down the street) do to people every day. Play games with your money. Here is the real deal. We live in the 21st century, cars have been made in a very similar fashion for a HUNDRED years. There is no, "well I guess it could be the radiator". Or "it might be the water pump". If you go anywhere that they need to guess, you need to go somewhere else. Because everything can be tested, EVERYTHING. And if anyone tells you different they are either lying or incompetent.
As always this isn't just for you Julie, it is for the people that may come by this post in the future.
Get everything documented as you go. People will tell you anything, but they won't write down their BS. Usually.
Always ask about a guarantee BEFORE the work is done.
There is always a recourse for bad work, if you have documentation. Get paper work, take pictures, check the work. Next time some says, "Well it needs a radiator mam". Afterwards mark the radiator with a Sharpie, or scratch an X in it, anything to ID it. And take a few pictures. THEN take it back for the work. And yes, I'm telling you it is a COMMON scam to just not do the work on cars that run. Or they will say 4 items needs to be done, and only do 2 of them.
And lastly take your case beyond them.
You can talk to a dealership manager until you are blue in the face and get nothing. Leave a bad review on their website or social media platform, and you would be AMAZED what can be done for you.
Next the Better Business Bureau, same thing.
And lastly, small claims court.
I really do wish you luck, but you need to make it happen. Todays world is nothing like when we were young.