They call and hang up

I've received 2 calls from this number, but since I don't recognise it I let it go to vm but they don't leave a msg.

It's one of those "you've been chosen for a free entry into a $200 gift card drawing" calls.
I said I wasn't interested

A new scam is out...someone will ask a question like "can you hear me" or "is this such&so"; if you say "Yes", then your recorded response will be overlaid in another recording which could be "do you accept this long-distance call" or "is your $1000 order correct"?  And then the fun begins...

They keep calling even after I told them to stop several times!!