call/alert me when I receive an SMS from a VIP
Found a partial answer, which will allow you to select a Sound. 

But not sure if I can set this sound to repeat until I turn it off.


Tap the Conversation you wish to set a custom notification for.
Tap the three-dot menu icon in the top right corner of the screen.
Tap Details.
Tap Notifications.
Tap Sound.
Tap your desired tone.
Tap the back arrow, or OK or Save if those options appear with your ringtone picking menu.


Source.