If they're doing some sort of pass through billing, contact your doctor's office to help out with this. I"m a bit confused if your doctor took your blood and sent it to the clinic, or if you went to the clinic. If you went to the clinic, odd that it would be a pass through bill.. meaning, the lab charges the doctor, the doctor charges you and gets a little profit... it should have just been a regular bill.
I'm having similar fun... our 16 yr old got billed as an adult for blood work, so it was denied. But, getting the right person to fix it.. that's the rub.
Pass-Through Billing Generally Not Permitted