Facetime audio icon missing
I recently got a (used) iPhone 6plus, transferring over my sim card from my old phone. It is 64gb, updated to 10.1.1 but the FaceTime audio only option is missing from the FaceTime app. I don't want to use the video call, just the audio only, like a phone call. There is only the video icon, no little phone call icon. Is it because of the update? Or is it hidden somewhere in my settings? Is there a way to get an old version of FaceTime so that I can use the audio calls?
Thanks!
iPhone 6 Plus, iOS 10.1.1