If there's a number currently on your phone's "Reject List" that you would like to receive calls from again, simply delete the number from your list. Locating the "Reject List" is often trickier than the actual removal process.
Select the "Menu" screen on your phone.
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Select "Address Book." Scroll down to "Reject List." Select this option.
Scroll to the phone number you want to remove. Push the key with "Select" above it on the phone.
Scroll to "Remove." Select this option.
Some phones have the "Reject List" stored in alternative placements. If the "Reject List" is not under your "Address Book" option, check under "Settings" and then select "Set Calls." The "Reject List" may appear as an option on that menu. Follow the same process after that point to delete the number from the "Reject List."