The previous iOS 12.1.3 had a serious problem known as “FaceTime Bug” that allows hearing the person you are calling even if they do not receive the call.
Apple immediately closed this feature after they knew about the issue. Apple then apologized for the issue and promised to roll out a fix in the next iOS update and now it’s here right now.
Apple has released iOS 12.1.4 for iPhone and iPad fixing the FaceTime bug. This means the FaceTime server is back online and now you can make FaceTime call as normal. Also, the fix has been implemented into the Group FaceTime call.
To update to iOS 12.1.4, head over to Settings – General – Software Update tab and follow the necessary instruction and if you have already enabled the “Automatic Updates” feature then the new iOS is already installed on your device. To check it, head over to Settings – General – About section.