Didn’t call back but there has been daily calls on numbers starting with 0488

Answered the phone and I can hear someone there but they didn't speak so I hung up since I think it's some nuisance call.

I keep receiving calls from this number and other numbers starting with 0488, they don’t reply when I answer and they don’t leave a message when I don’t. I blocked them but I still get calls from similar numbers.

Caller: Probably Open Agent

I made the mistake of checking the Open Agent website and then unsubscribed. Since then have had daily phone calls from numbers starting with 0488. All seem to be from open agent. No message left. Hang up when I answered the first time.
Yesterday I replied STOP to the number and said 'from ANY of your numbers' - yep, another 0488 call today. Reported them to ACMA.

Recevied 2 calls today but no-one spoke when I answered so, checked this link and as a result blocked the caller who is/are obviously spammers