Block this number... Using illegal tactics , probably gaining access to others mobile phone contacts.

I called back number (02) 8651 5193 spoke to a guy who said company name is Credit Corp.

Debt Collection Agency - Dun & Bradstreet

Legit - Debt Collection Agency.... Dun & Bradstreet.... But you probably want to block the number and call them on your own terms.

Debt Collection Agency.... Most likely Dun & Bradstreet. If you call the number back, the wankers won't tell you who you've called. They give you the "this is the switchboard for multiple companies... Just give me your details and I can look up who was trying to call you" bullsh*t.