ive found telstra very accomodating with these wackos. there is no point calling them back. chances are its a call centre and wont connect you to anyone.
youll be hard pushed to get the person who called you again.
most companies not use a computer to dial, when they have a person ready they grab the call and talk to you, if they dont have a person ready it simply hangs up on you, hence the reason you get alot of blank hang-ups.
we were getting up to 2 a day, we got a trace put on by telstra. it was about $5 for the month. when they rang all we had to to was answer it and if it hangs up (or they talk for that matter) keep the phone off the hook, connected to the caller for about 5 mins. give telstra a quick call with the exact time and details of the call tehn they look up the number. in our case they traced it to a telemarketer. they wont give you the number but can have your number removed from the telemarketing companies call list. legally, and they wont call back. we were lucky it was only one call centre calling, and we caught them out. $5 well spent i reckon.