Once a voicemail is received, it is the onus of the recipient of the voicemail message to call the caller back when a “missed call” message is received on the phone or after the voicemail message is retrieved. While some of the more advanced voicemail systems provide the capability of automatically...http://www.google.fr/patents/US8150003?utm_source=gb-gplus-shareBrevet US8150003 - Caller initiated undivert from voicemail
