Apple's iPhone includes a preference in the Settings application to easily turn on and off call forwarding. This is handy if you want every call forwarded to another number, but this is often not the case. What if you just want missed calls to forward to another number? You must dial in this setting to set it up on your phone. Creating a contact with the call forwarding information is an easy way to quickly access and set up your conditional call forwarding.
Open the Contacts application on your iPhone. Set the contact name as "Call Forwarding."
Determine the number you are going to forward the call to.
Add a phone number to your new Call Forwarding contact. The number should be:
_61_CALL-FORWARD-NUMBER# (replace CALL-FORWARD-NUMBER with the forwarding number).
Save the contact and quit the Contacts application. Using the 61 command will forward all unanswered calls. Use 67 to forward if your phone is busy or 62 to forward if your phone has no service.
Open the Phone application. Select the "Favorites" button in the bottom left corner of the Phone application. Select "+" button to add a contact and pick the Call Forwarding contact you just set up. You can now easily turn on call forwarding by selecting it from your Favorites list.