You can delete a number from your list of barred numbers. You can check your list at any time. To do this, dial 14258 and enter your PIN. Choose to Refuse gives you a choice to review your barred number list.
Choose to Refuse tells you the number and the date that it was barred. You then have the option to delete the number from your list.
You can only bar 10 numbers. The 11th entry replaces the oldest telephone number stored. Check the list of barred numbers (see above) to ensure that you have not exceeded the maximum number.