Dental Office Wants To Charge Me Uninsured Price For A Visit 4 Years Ago

location: Illinois

I received texts from my old dental office stating they performed audits on old accounts and discovered I had a balance of $252 for a visit back in Sep 2022. They state insurance denied this visit's charge and the dental office wants to setup a payment plan. We never were notified of this balance until two weeks ago.

After some research, I discovered the coverage was denied due to 'coverage not active' because they were trying to charge my current dental insurer which started coverage on 1 Jan 2023. I provided the dental office with the old insurance information (different provider and account numbers) which was active since Aug 2022 and covered the visit in question.

The dental office now claims they cannot charge the older insurance company due to "insurance timely filing policies" and claims I'm responsible for the full cost. They stated their intent to send this to collections if I don't pay the full $252.

I've offered to pay a standard copay amount, but I don't think I should be responsible for 10x that price because this dental office didn't inform me of the balance until now and waited too long to allow the proper insurance to be billed. This feels like making me pay for their mistake. I'm still waiting for their response to this offer.

I don't think I should be liable for this increased cost, but also don't want it to go to collections (I assume there's negative effects to have that on my record).

What legal options/pushback do I have in this situation?