(03) 9015 7375 - I called the number back and reached The Smart Group. Based on the IVR, they are calling to inform customers about Telstra's product and services. It was just an automated system and no live person to speak with. In the IVR, an opt out option was provided. To opt out, dial 1800 039 059 between 9am-7am AEST excluding public holidays.

Exactly the same happened as in Anna's case

It rang two times then hung up... Just so they don't have to spend the money for the phonecall.

I called the number back and a recording answered, "Data Solutions, leave your number and we'll call you back later..."