Luckily Samsung made blocking calls & texts on the Galaxy Note 3 pretty easy.

Here's how to do it:
  1. Hit the phone icon
  2. Menu > Call Settings
  3. Call restriction
  4. Auto reject mode on
  5. Auto reject list
  6. Create - add the number or contact
  7. You can Match criteria like "numbers that begin with 123", for example

See More: Galaxy Note 3: Block calls & texts