Strange call from Telstra

Yesterday while sitting in the study, I received a call on my mobile. The number was a 039 number, which means in Australia its from Melbourne.
I answered the call and at first heard nothing. Then, I started hearing a standard dial tone -- the one you hear when you're waiting for the other person to pick up the phone when you have rung them.
This went on for about 10 seconds, and then... the phone picked up. On the other end of the line I heard what seemed to be outside trafic noise, or a train station or something... and then a young voice, said "Hello?".
I was rather confused and hung up my mobile very quickly, which I'm sure the young person on the other end thought was quite rood I guess.
I started to think... did I miss that other call, and then accidentily bump something on the mobile to ring that other person? surely not.
I then looked at my call history on the phone, and sure enough, all that had happened was one incoming number, that 039 number. There was no outgoing call after that.
I was very curious, so I rang that 039 number again.
What I heard, was a message that went something along the lines of:
"Hi, we've just tried to contact you to talk to you about products and services from Telstra you may be interested in. If we did not reach you, we will try you again soon. However please feel free to leave a message."
I hung up.
So, I guess, though this does seem rather impossible, that Telstra tried ringing me and Then I answered the call right that the very point there system gave up on my call and went to ring some other person. However, the system for some odd reason routed that new call to me, rather than to the sales rep at Telstra.
Very strange!