I have a Nokia 920. To remove call+SMS blocker:
1. from the home page, click the phone icon
2. touch the elipses at the bottom right (...)
3. touch blocked calls
4. touch the blocked numbers box
To unblock one contact...
5. long-touch the number you want to remove from the blocked list
6. touch unblock
(verify a confirmation in the header that the number is now unblocked)
To unblock more than one,
5. touch the selection list icon (bottom middle of screen)
6. select the numbers to unblock
7. touch unblock
(verify confirmation in the header that the numbers are now unblocked)