Persistent calls then hang ups

I don’t recognise this number so I didn’t pick up. No message was left on my voicemail

Caller: (07) 3741 6375

Called back as I was expecting a call and it answered I explained I was returning a call and he just hung up

Calls nearly everyday

has called 2 day in a row and I hve not answered - no messaged left

Caller: ACF

Claimed to be ACF asking for monthly donations to help with their environmental campaigns, thanked me for signing their petition. Don’t remember doing this, unsure if call was legit.

yes very persistent calls

Multiple missed calls, hasn't left a voicemail.
Have tried calling back several times but I am instantly diverted straight to call waiting/music and eventually it just times out.

Suspected telemarketer or scam so have blocked the number.

Caller: Wildlife fund?

Called asking for donations. They did seem legitimate and spoke to a local guy but they have been a bit persistent in calling.