First, activating International roaming but disabling mobile data so that you can receive free SMS.
Secondly, diverting all mobile calls to your DID. I use Pennytel $5 Freedom plan which includes 150 untimed international calls, 50 worldwide texts and 1 DID. Skype-in numbers work too. Buy a Skype Gift card at 50% sale to save.
Thirdly, diverting all calls to your DID to a local sim of the country you are travelling to. Your VoIP plan would cover the international leg of the calls.
I can receive calls on my mobile while overseas without paying any International roaming fees. The call quality is excellent.
thank you. Very useful. What is DID?
Must the call divertion done before you leave Australia, in that case, how do you know the local sim number?