From the Start screen, tap the Phone tile. Note: The call blocking feature may not affect phone calls made or received via third-party apps installed on your device. Please contact third party app developers for assistance with such applications.
Tap the Menu icon, then tap Blocked calls.
To block a number, tap the Menu icon.
Tap Block list.
Tap the Plus icon.
Enter the desired number then tap Block.
To unblock, touch and hold the Desired number and tap Unblock number.