Natera billing after hitting out of pocket max

I am in California. Aetna HDHP till Aug-31, PPO thereafter

I hit my OOP max of $3000 for a bunch of tests (pregnancy diagnosed with fatal issues – MRI, bunch of advanced tests, termination etc.).

When I was tallying my health insurance claims with the bills from providers, I noticed that I had paid $500 for two tests to Natera (genetic testing company) back in June. Natera is in-network for my insurance provider Aetna, so I wondered why I don’t see a claim on Aetna. This is even more important now because I have already hit my OOP max, and I’ve technically paid $3500 OOP at this point. When I called Natera to inquire, they said that I had chosen the “self-pay” option and already paid for the tests so they didn’t submit a claim to insurance.

I insisted that they submit a claim now, because technically I shouldn’t be liable to pay $3500 OOP. They first argued with me about it a lot, then said that they can put in a claim now, but if it gets rejected by my insurance, I might be liable for the entire $8k. I don’t understand this — first they said the self-pay option is for $500, and now when I asked them to go through insurance, they were very defensive and said that I might be liable for $8k. I was hoping to reduce my bill by $500 but now I’m scared they’ll charge me $8k.

Should I ask them to withdraw the claim? Would I be liable for the $8k if it gets rejected?

PS I changed employers in August, and the new employer’s health insurance cycle ends in Nov. I had all my tests and procedures between Aug-20 and Sep-10 and ended up hitting the OOP max for both cycles, and I’m out $6k in that one month, so reducing the additional charge of $500 would be really helpful