Missing Contacts in iOS

If you deleted your email account profile from the built-in iOS mail app and installed it on Outlook for iOS instead, you may no longer see your contacts in the iOS contact app or phone app.

To fix this:

1. Open Outlook.
2. Tap the Outlook main menu icon.
    
   
   
   
3. Tap the Settings icon.
   
   
   
   
4. Tap your email account. 
5. Enable Save Contacts and tap Save to My iPhone.