 X is rolling out audio and video call capability, at least to some users. Some X users reported a new notification when opening up the app that says, audio and video calls are here. There's a new enable audio and video calling toggle with the app settings. You can turn the feature on and then select who you're comfortable with using it with. X hasn't officially said more about the audio and video calls feature, or if it's going to be available to non premium users.