Carbon Health Billing Years Later

I received a bill from a Carbon Health Urgent Care for services rendered almost 2 years ago. I sent an email asking why I was getting charged when my insurance should've been billed.

They claimed my insurance "never responded" to their claim. I've had many a doctor file a claim and they always received them. Now it is true my insurer never received a claim, I see no record of one in my history, but it is also true that the office had my insurance info and validated it. I double checked after receiving the bill. So my instinct is saying they never billed and are now trying to pass the buck off on me. Or they improperly billed and are trying to make it my problem.

I see one message I received about needing to comfirm insurance or I'd be billed in full about a week after the appointment. Which I'm assuming I did because it was radio silence for almost two years, and all the info listed online is correct. This bill was recent, it wasn't sitting unpaid the whole time.

Anyone else run into issues with this company? If so, what did you do? I'm in California not sure if that offers additional protections or if there's a statute of limitations for how long they have to bill an individual (not insurance I know there's rules for that).

I will be filing a complaint once I figure out who to file with. Their help people kinda waved off my concern and they have my credit card saved (I couldn't delete it) So I imagine I'll be charged soon and I refuse to just ignore the aggregious timeline and lackluster explanation of this bill.