How do I restore contacts from iPhone backup?
To bring back lost iPhone contacts, just check the Contacts box, then all contacts will be displayed, simply choose those contacts you'd like to recover, and press "Recover" button. Now, you will get two options, "recover to computer" or "recover to device".
Why did I lose contacts on my iPhone?
So go to Settings > Tap iCloud > Find Contacts> Toggle it off if it is on, and then toggle it on again; While if it is off, turn it on > Then iCloud will ask you if replacing your iPhone contacts with iCloud contents, select Delete from My iPhone. And your contacts will get back again.