I called back number (02) 8651 5456 spoke to a woman but did not say from what company.

Not spam - legitimate debt collection/ specialty finance company - CREDIT CORP. They will only be calling you if you have an active account or debt with them. They are generally pretty good to deal with compared to some other companies.

debt collector

I called back number (02) 8651 5456 rang 2 times then goes to busy tone.