Tap Settings.

Tap Phone.

Tap Call Forwarding.

Choose one of the following options:
Turn on divert, go to 2a.
Turn off divert, go to 2b.

Tap the indicator next to "Call Forwarding" until the function is turned on.

If it's the first time you divert calls:
Key in the required phone number and tap Back.

If you've diverted calls before and want to change the phone number:
Tap Forward to.

Tap the delete icon to clear the text input field.

Key in the required phone number and tap Back.

Tap the indicator next to "Call Forwarding" until the function is turned off.

Tap the Home key to return to the home screen.