Select your Contacts from your home screen.
In Contacts, tap the three dots in the upper right to access your menu.
In menu, tap “BLOCK CONTACT”.
This will bring up a screen with all your blocked contacts.
You will see the number that can't text or call you as being blocked. Simply select that number to unblock them; the screen is very simple to use.
Exit Contacts.
It took me weeks to find this simple silicon, because I never blocked the number I was having trouble .