I have an iPhone 7 and I installed iOS 12 on it. In iOS 11, in Facetime, I could choose between FT audio or FT video. Now, I don't see that option to choose between making an audio call or video.
Facetime Audio?
Go to your contacts and select someone who has an Apple device and you will see a FaceTime section in the contact-details, which shows a camera and a phone-symbol next to it. The phone symbol takes the FaceTime-Audio call. You can also ask Siri "FaceTime Audio Mr. Smith".
file a bug too!