Looking to permanently block a phone number on the iPhone? Apple has added this built-in functionality to iOS 7. Contacts and numbers on your iOS 7 block list will be prevented from contacting you with phone calls, iMessages, SMS text messages or FaceTime.
To add a contact to the block list in iOS 7 follow these instructions:
1. Navigate to Settings -> Phone (or Messages, or FaceTime) -> Blocked
2. Touch Add New...
3. Select the contact you wish to block from the list
To block a phone number that recently called your iPhone:
1. Navigate to Phone -> Recents