Pjing, XBT, etc--Please help! Advises needed: medical examinatio

Just found out the doctor who did the examination for me is not in USCIS list! I made the appointment with one who is in the list, but the one who actually did the exam was someone else!! Called the clinic. They insist all their doctors are certified and qualified to do such a test and refused to let one of the two in the list sign the paper work. Any idea? What should I do? Please advise... Thanks...