0411 934 000 this number called me at 3 in the morning

This number showed up in my phone.

I tried to ring back and the announcement says, "Optus advises that the number you have dialed has been disconnected. 03REM..."

I know the number is a mobile number, but the recorded announcement seems for a landline number. Could the mobile be diverting calls to a disconnected landline or fixed line number?

I have received similar calls before and received the same recorded announcement.