How to disable Facetime
Step 1: Check to see whether you’re susceptible: Make sure your iPad or iPhone was affected by the glitch. It exists on iOS devices with the most recent software updates, starting with iOS 12.1.
To check your iOS version, open the “Settings” app, scroll down and select “General,” and then click on “About.” In the following list, you'll see a line titled “Version” followed by the operating system on your device. If your iOS is 12.1 or newer, such as 12.1.3, your device could be at risk.
It’s not clear if the glitch is also affecting Apple computers, but the Group FaceTime feature was recently introduced on them with MacOS 10.14.1. Check the current version on your Mac by selecting the Apple icon in the top left of your screen and clicking on “About This Mac.” The latest version is MacOS 10.14.3.
Step 2: Turn Off FaceTime: On an iOS device, open “Settings.” Scroll down a bit until you see “FaceTime” and select it. Tap the green button on the top row, which will toggle FaceTime off. The button should turn gray, and everything that had been below should disappear.
To turn off FaceTime on Macs, open the app, select “FaceTime” at the top left of the app, and then select “Preferences.” Click on “Sign Out.”