Received 3 calls in 3 hours and no message left. When I try to call back, I only get static

Just got a call from this number, no message was left. The phone rang about 4 times and hung-up.

they have been calling nonstop for two days. any ideas?

From online survey depending on your lifestyle answers/ choices.

I just hang up with someone fromm this number. Saying that I qualified for 1 million dollar sweepstakes  and it was only between and another person. But they needed to verify my credit card number. So that's when I saw it a little suspicious and told them I didn't have it right there they said I was disqualified and then hang up on me.