D-Link DWR-922 User Manual page 42

Section 3 - Configuration
Click Add to configure a new call diversion (forwarding). More
settings will appear.
Add External Call Check Active External Call Forwarding to enable the new rule.
Forwarding: Enter a Name of your choice, and enter the Forwarding Number
to forward incoming calls to. Finally, select the VoIP account that
the rule should use, under the Connect via drop-down menu.
Click Apply when you are done.
D-Link DWR-922 User Manual
External Call Forwarding
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