Year-old corn snake

[Bogertophis]

I would either ask the store to pay for the vet, or have them treat it until its healthy. If neither of those would work out I would get a refund.

I don't believe they didn't already know it's sick, & since they said they have medicine for it & offered to treat it, I'd also bet they've already treated it, & the
infection probably returned.

That's another thing...if YOU take the snake to the vet, you should know WHAT the snake has already been given, as additional treatments can be harmful (hard on the
snake's liver). Antibiotics are not 100% safe for reptiles...being given the wrong ones or being given them incorrectly can cause resistant germs, making success less
likely. Repeated treatments with different antibiotics are not without risks for the snake. It's possible that if they dose it again, it may seem to clear up for a while,
only for the infection to return again later...when you're stuck with him. Just saying... Hope I'm wrong.