How to activate Three Wi-Fi Calling on iPhone
Go to Settings > General > Software Update Download and install any software update that pops up, if none, move on to the next step If you do install a new software update, you may get a notification to update your carrier settings, if you do, select “Update”
Go to Settings > Phone Select “Wi-Fi Calling” Toggle “Wi-Fi Calling on this iPhone” switch to the on position Confirm that you want to activate the feature
Go to Settings > Mobile Data Select “Enable 4G” Select “Voice and Data”