@Jacqueline955 When a booking is confirmed, the guest receives the phone number you have on file automatically, as their number is also visible to you.
So all you need to do when a guest checks in is make sure they have that and know they can call you if there's an emergency, but for non-emergencies to please use the Airbnb messaging.
The number you see when you get alerts from Airbnb has nothing to do with communicating with guests. If they message you through the app, you should get an alert about that, and if you want to be available by phone if the plumbing bursts in the middle of the night, then you'd add the guest's number to your lists of non-Do not Disturb numbers.
If a guest calls or texts you and you feel it should be documented on Airbnb messaging, just follow it up with a message-"Hi XX, to follow up on your call this morning, saying the hall light isn't working, I can come by to check it out at your convenience -would noon be okay?"