Dentist Retroactively Charging Me $400 After I Paid In Full — Do I Have Any Options Left?

Location: central Texas

Hi all, I’m looking for advice because I’m feeling pretty stuck and anxious about this situation. This might not be the best subreddit so please tell me if I should take this down !

Back in December, I went to my dentist (Fusion Dental & Braces) and was quoted for a custom night guard. I asked multiple times whether my insurance applied, and I was told clearly that insurance did not cover it at all and that I would be paying out of pocket.

I was given a written quote for $265, and then verbally told my total responsibility would be $315, which I paid in full on the day of my appointment (December 4). I would not have agreed to the night guard if it cost significantly more, obviously!

On December 31, when I went to pick up the night guard, the front desk staff confirmed again that I had paid in full and that my balance was $0.

Then in January, I was notified that they were retroactively charging me an additional $400 (bringing the total to ~$715–$800) because of an internal “insurance or pricing issue.” They said insurance didn’t cover it, but I had already been told that insurance never applied in the first place.

I disputed this in writing (email) and explained:

• I was quoted one price
• I paid in full based on that price
• I relied on that representation to consent to treatment
• I would not have agreed at the higher price
• I still have the original written quote and proof of payment

My email went unanswered, so I called a few days later to follow up. They told me they would talk to the regional manager and call me back within 3 days. Nine days passed. Today, I called again and was told the regional manager is now requesting that I pay in full. The woman I spoke to on the phone (who quoted me, originally) kept apologizing over and over again since "the system" pulled up the wrong price to begin with and "she takes the blame".

So now I’m wondering:

• Is it over at this point?
• Can they legally retroactively raise the price after confirming I paid in full?
• What realistic options do I still have (formal disputes, complaints, etc.)?

I’m not trying to be difficult, I swear. I just feel like I’m being charged for their internal mistake and it’s stressing me out since I'm currently saving everything I can for law school. $400 is a lot of money in this economy!

Any advice on next steps would really help!

tl;dr Dental office quoted me $265 (then $315, which I paid) for a night guard, confirmed I was paid in full, then a month later tried to add an extra ~$400 due to an “internal pricing/insurance mistakes.” I disputed it in writing, regional manager is now insisting I pay in full anyways. What are my options?