Nokia Lumia 830

Find "set"

Slide your finger down the display starting from the top edge of your phone.
Press ALL SETTINGS.

Find "set"

Press network+.

Find "set"

Press set.

Select divert type

The current settings are displayed.
Press the field below one of the following options:

Select divert type

All calls

Select divert type

When I don't answer

Select divert type

When I'm busy

Select divert type

When I can't be reached

Enter the voicemail number

Press enter number.

Enter the voicemail number

Key in (prefix) 5 (your phone number) and press the confirm icon.

Divert calls to your voicemail

Press the divert type until the function is turned on.

Return to the home screen

Press the Home key to return to the home screen.