Tap Phone.

Tap the Menu key.

Tap Call settings.

Tap Additional settings.
After a moment the current settings are displayed.

Tap Call forwarding.

Tap Voice call.

After a moment the current settings are displayed.

Tap each of the following options:
Always forward

Forward when busy

Forward when unanswered

Forward when unreachable

Tap Disable.
Repeat until all diverts have been turned off.

Tap the Home key to return to the home screen.