Further to my last comment, when I called back they said they were "Call Active". I think a scam pretending to be Telstra.

Glad I goggled this no and read the replies
Has been trying my mobile a fair bit
I just blocked this no

I had two missed calls yesterday, and one today from this number on my mobile. All three times I purposely didn't answer and waited to see if they would leave a message - they didn't. I now have this number on my auto reject list.

I think this is a scam. Called a couple of times wanting you to call back. No response except voice saying they will call again later if they didn't get u, and then don't call back, or message saying disconnected.