From now onyou can receive SMS or e-mail notifications about the missed calls in case the phone with BusineSim is out of coverage area or turned off.
SMS notification is sent when the phone is unavailable for a period up to 4 hours, e-mail is sent regardless of time period to the e-mail address attached to voicemail (if available). Notifications of missed calls are sent upon incoming/outgoing call or in case the roaming country changes.
If the caller left Voicemail message, the notification of missed calls will not be sent because you will be notified about the new voicemail message anyway.