Keeps calling and leaving messages with nothing in them

Caller: I don't know

3 phone calls and no messages left

Scammers. Pretending to be NAB in order to get your data. DO NOT confirm your name or any of your info. Just hang up.

Said to be NAB and asking re overdrawn a/c. Had all the patter "this call may be recorded" etc etc.

Caller: supposedly from NAB

Long delay in them speaking, They ask for someone who works here, but I am very sus, so put them on hold, ring the number and it says you have rung the NAB group of companies. The person on hold only waits about 20 seconds and then hangs up. SCAM

6 times I have had a call from this number. No message. I answered once with no-one at the other end.