Rename Your Messenger Room (iPhone)
Open Messenger App.
Tap Your Rooms.
Tap on the three dots next to your room’s name
Tap Edit Room.
Tap Room Activity.
Tap the + icon.
Type in your desired name and select an emoji to go with your name. Once you’ve finished this step, hit the Done button on the top right side.
Hit the Save button on the top right of your screen. You have successfully renamed your Messenger Room.