New iPhone SE
Just got a new SE and for some reason the iMessage is only appearing as SMS Texts. Why? I would go back to the Apple store to ask but .... good gawd I was already there for a big chunk of my day!!!
iPhone SE (3rd generation)
If you can’t turn on or sign in to iMessage or FaceTime - Apple Support
Make sure that you have iMessage enabled by going to Settings > Messages. If you see "Waiting for activation...", be patient; iMessage & FaceTime can take a few hours to activate when getting a new device.
Contact support if iMessage isn't activated tomorrow.