[wdfifteen]

Ah, mystery solved. I had restarted the iPad because of another issue and somehow it turned iMessage on for me when it restarted. Very helpful.
Thanks for your help.

edit:
nope. iMessage is off and the banner was gone for a while, but now it's back. I'll restart again and see what happens.

edit: it's back. I tried with cell data on and iMessage off - won't go away. Turned cell data off and iMessage off - won't go away. z