Caller: I don't know

unknown caller, did not leave a message. potential scam.

No message left - Called back and went straight to 'All our operators are busy please leave a message' without saying who they were

Didn’t leave a voicemail

Missed call. They did not leave a message. Called back (awaiting contactors) and it went straight to a voicemail with no company name.

Very dubious.

I missed their call so I rang back and there was a voicemail saying:

"thank u for calling, all our agents are busy right now but if you leave your name and number i'll get back to you".

Doesn't reveal her name, where she's called from, and wants your details..LOL!!

Caller: I don't know

Unknown number to me so I didn't answer. No voice message left so assume hoax.

Caller hung up after I answered the phone.
Likely a scam