If you have a BigPurpleSIM, it uses Telstra MessageBank for voicemail. When you first dial Voicemail, you will hear the message: "Please enter your new PIN followed by the hash key". It is asking you to set up a new PIN.
The PIN is only required when you call into your Voicemail from another line, say your home, work line or a different mobile.
You do not need this PIN when listening to Voicemail on the BigPurplePhone.
To set up the PIN -
1: Enter a new 6 digit PIN, then press #
2: Enter PIN a second time to confirm
3. Hang up