Repeatedly spamming me also along side (02) 8014 8844

I have had 2 prank calls to my mobile in the last week from this number, but when ringing back to that number, the message says it is not a valid number and to check the directory!! Wonder how they can call from that number but it is not valid. Maybe a computer generated number??

Scam
Missed call. Unknown caller. Similar pattern (time of day, quick termination of dialing) to recent calls from (02) 8705 3274, (02) 4602 6003, (02) 9346 4500,(02) 8404 0627