I answered a call from this number but it was music on the other end.

This looks like a generic call-centre CLI number in Sydney - they must perform a variety of services. The person called me about some prior work I had requested with Amaysim (www.amaysim.com.au) so sounded quite valid as they would not have called me unless what they described is what I needed.

I called back number (02) 8035 4100 reached voice mail for a company called Hosted Contact Services.

I called back number (02) 8035 4100 reached voice mail but did not say from what company.

Call centre charity fund raising. 9 calls over the past 2 weeks. Block number on mobile.
Charity careflight.

I rejected the call then called back from a private number to check it - it said that "You have been called by a hosted calling service, you may be called back in the future"
Another number to block...