Caller: debt collectors or some nefarious others

Ditto same experience. Professional corporate voice message to call back during business hours. What sort of company doesn't identify themselves when they are legit?
Feels like prior experiences that when you do manage to speak to someone they remain reluctant to identify themselves but want your details first. Debt collectors or professional scammers of the type.

I called back number (02) 8897 0821 reached voice mail but did not say from what company.

Caller: They were very muffled trying to announce who they were.

I missed a call. Called back. Muffled in replying with who they were but definitely needed my name. They said there were no missed calls to my number and that if there was, they would've left a message but no message was left.