Number goes straight to voicemail when you try to call back. Have blocked it now

Caller: 0453576233

Told me they were a law firm contacted with the tax office

They said they were from NBN and that there was a problem with my internet connection. I asked them if they were Telstra. After hesitation, they said yes. I told them that Telstra wouldn't call me and then hung up. Obviously a scam

they called me,no voice message, no SMS, unknown, think spam while being in the city (Sydney)

When you call this number back it automatically goes to a voicemail. Do not answer - spam/fraud

I returned a call from 0452 613 767 but the voicemail didn't mention the company name