It is possible to call back a restricted number on a cell phone or land line by dialing *69 as the next action after receiving such a call. This only works in situations when no other calls have been placed or received since the restricted contact.
A restricted number or private number is one that is intentionally blocked by the caller for a number of personal reasons. This prevents the caller's phone number from appearing on caller ID, and this information is not recorded in missed call logs or in voicemail messages. Such communications make getting back in touch with the caller difficult unless other means of contact are available or the person's contact information is known to the recipient.
When neither of these conditions is applicable, it is possible to call the restricted number back as long as there are no other actions on the phone since the restricted call was received. That means no voicemails are retrieved, no outgoing calls are made and no incoming calls captured since the restricted number. Simply dialing *69 connects the caller to the last line that established a connection with the cell phone or land line in question. This works in a majority of cases but does incur charges for usage, depending on service provider and other carrier restrictions.