Insurance Refuses To Pay Labor/delivery Bill Claiming It Was Submitted Out Of Allowed Timeframe

My insurance company is refusing to pay my daughter’s labor/delivery bill claiming I submitted it outside of allowed timeframe.

My daughter was born at the beginning of August. She was added to my insurance at the beginning of September (within the 60-day allowed major life event change enrollment period). I have paid the additional premium price every month on time since she has been added, and all other doctor’s appointments have been successfully submitted and verified through insurance.

Since the beginning of September I have made multiple attempts to file her hospital labor/delivery bill, but it has been denied again and again by the insurance company as they claim my daughter could not be found in the system. I have spent hours of my life on the phone with the insurance company, the hospital billing center, and sometimes a 3-way call between the two. On multiple occasions, the billing company has submitted an incorrect member ID and cannot verify her insurance. On other occasions the member ID is submitted correctly but the insurance company does not recognize her as a member. Again, she has been a member since the beginning of September and I have paid all the monthly premiums on time.

The hospital billing center has kept a detailed log of all phone calls and in this log it shows that I have been attempting to file this claim since September.

After an escalated series of phone calls before the holidays, the claim was FINALLY successfully submitted but NOW my insurance company is claiming it was filed outside the allowed time frame and recognize it as officially filed at the end of December, even though I have been trying to file since the beginning of September.

I am at my wits end with this. Do I need to hire a lawyer, and if so where do I look/what do I do?

Thank you Reddit community in advance

EDIT: her coverage was backdated to her birthdate, so she is covered from the day of her birth.