Calls but does not speak when call is answered

have the same issue from this number and a sequence with last numbers 954, 962. 961,959,957,956

Repeated hang up calls

Claimed to be from Sydney.
Knew my first name & email address.
Said they'd sent me an email & tried to sell me something, but couldn't understand them.

Missed call left heavy breathing think scam

Called me but when picked up just here background sound and hangs up 20 seconds later. I tried calling back but says number is not connected.

Called but did not speak. Recording my voice?