You will be billed for the appointment. You can choose to go to another GI if it is okay with your insurance. Just explain to your PCP that you didn't feel comfortable with that GI and you would like to try another. If that upsets your PCP, then honestly you need a new PCP!
"For this thing I besought the Lord thrice that it depart from me. He said, My grace is sufficient for thee: for my strength is made perfect in weakness. Most gladly therefore will I rather glory in my infirmities; I take pleasure in infirmities, reproaches, necessities, persecutions, distresses, for when I am weak, then am I strong" 2 Cor