How to remove Your carrier may charge for SMS Messages used to activate FaceTime

This message keeps coming back: "Your carrier may charge for SMS Messages used to activate FaceTime" I managed to get rid of it before but when I change the SIM card it pops up again. It's similar to "Your carrier may charge for SMS messages used to activate iMessage", which I got rid of this time but I don't remember how. How to quickly ensure both these messages don't pop up: - Your carrier may charge for SMS messages used to activate iMessage - Your carrier may charge for SMS Messages used to activate FaceTime Ideally forever, but I'm ok with a quick solution that I can quickly find back here on Ask Different. Oh and I want to keep Facetime enabled. Not sure about iMessage.