How do I block this caller’s number after I have deleted the message on my phone that they called

Caller: Aussie Saver

I received this call today and the guy (with a non-Aussie accent but talks like a robot) identified himself as from Aussie Saver. He told me that I won a $1000 Aussie Saver voucher from an online competition. I told him that I never joined those competition as I always receive a Sales call. Then he said (in robot-like tone), "We will join (?) you to the Aussie Saver $1000 voucher competition and we will call you if you win so keep your mobile handy. Alright ?" I said, "thank you but I'm not interested". Then I hang up and block this number.

they rang to say I had won a coles gift card knew my email cant remember entering a competition

Same here. Automatically disconnects call.

I called back number (03) 9109 7290 rang once then gets disconnected automatically.