I've just had a stack of calls from different numbers constantly for 30 mins:
(02) 6190 7641
(02) 9157 2800
(02) 9157 6328
(03) 7065 8851
(03) 7065 8866
(03) 7065 8885
(03) 7065 8889
(03) 7065 8890
(03) 7065 8899
(03) 9969 6415
(07) 3187 8513

They all seem to be fax calls, all have left a VM of varying lengths (up to 5 mins long) which are just beeping noises at ~3 sec intervals.

Could be rogue Fax machine but likely scam call of some sort? - answered incoming call from an (08) number first/just getting a repeating 'tone' like a fax would give waiting to be switched to the receiving fax (if you know/you know) ... BUT once I hung up, I then got THREE MORE identical calls, less than 30secs after I hung up each time .. from 3 different (07) numbers? - this being one of them .. THEN about 5mins later got another incoming call/same thing but from an (02) number ... VERY ANNOYING