text message notification about missed calls

Depend on your phone brand and  Phone Dialer I'm using Google Phone dialer  and this option is not selectable. 

You may have to go to settings first then the following. 

       1.Phone. 

       2.Tap Phone. 

       3.Tap Notifications. 

       4.TapMissed calls. 

       5.Edit the notifications you want. 

Or this very similar. 

1. Go to Apps.
2. Tap Settings.
3. Tap Notifications.
4. Scroll through apps until you find your Phone app, tap Phone app.
5. Tap Missed calls.
6. Set what kind of notification you want or toggle, so all grey to disable.

😉