how can i get a deleted message back

I'm sorry, I provided you link please click on it and read it. It answer all these question your asking.

The fact that you're asking these question leads me to believer you've never backed up to icloud or itunes before.

if you back up then do this Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Click on the link I provided in my original response.

the main question is do you back up to icloud or itunes.

IF you've never backed up then there is nothing to restore, that message is gone.