About two minutes on your handset. Do these in order.
The order matters, and getting it wrong looks like success
##002# cancels every diversion on your handset, including the one you are about to set. So it goes first.
Run it last and it silently cancels the divert you just set up. Your phone looks completely normal and catches nothing at all. This is worth being careful about because there is no error message and no obvious symptom.
The sequence
##002#clears every existing diversion, including carrier voicemail- Turn carrier voicemail off. See the carrier page
**61*<your number>#diverts when you do not answer**67*<your number>#diverts when you are already on a call**62*<your number>#diverts when you are out of range or switched off*#61#reads back what is set, so you can check it took
Use the number I give you in place of <your number>.
All three conditions, not just “no answer”
It is tempting to set only the no-answer divert. Do not.
The call that arrives while you are already on the phone is usually the one you most wanted caught. So is the one that arrives in a basement or a shed with no signal. Those are **67* and **62*, and they are the two people leave out.
Do not set a custom ring timer
Your carrier’s default is fifteen seconds before a call diverts, and that is what we want.
There is a version of the code that sets a custom timer. Leave it alone. The syntax is easy to get subtly wrong, one major carrier publishes syntax that contradicts itself, and another cannot set the timer by dial code at all. If fifteen seconds genuinely does not suit you, ring your carrier and have them change it: Telstra 132 200, Optus 133 937.
Turning it off again
##002# cancels all diversions and puts you back exactly where you started. Your own number was never modified, so there is nothing else to undo. Full instructions here.