That’s what the Clever Dialer block list is for. To open the block list, press the menu icon in the top left corner of the Clever Dialer app. In the menu you will find the item blockings, which contains the block list. To mark the phone number you want to “unblock”, it is sufficient to press a little longer on the corresponding list entry. In the top right corner you will see a trash icon. As soon as you press it, the phone number will be removed from the list and will no longer be blocked.