This is how screwed up my HMO is:
when I called about this unpaid bill on Friday, I was told by a customer service rep that the referral physician had not sent a referral request for the X-rays and I needed my primary care physician to submit a post-dated referral. I sent my doctor the request for a post-dated referral on Friday. When I got home last night, Dr Teng's email said that it was too late and she could do nothig.
Just now, a customer service rep told me the whole shebang was paid on May 18 and I am off the hook. She gave me a reference number!