We made arrangements with Optus to meet a technician on site after we took up residency at a retirement village. Since then we have had several calls from this number to "confirm appointments" to meet technicians on site well before we made our big move. After the first call I re-confirmed our original arrangement. I have no doubt these calls are from a group with ulterior motives
I had a call from this number 03-9001XXXX and it was the NBN call centre who left a voice message on my mobile. They said they were connecting our NBN in 1 day, That being the 06/01/21. This was true as we were connecting the NBN on this day and their call was a reminder call of the connection. It was and O/S call from say India or somewhere.