This number called me twice today. The number looked suspicious.
The first time the number rang, I answered and didn't say anything. I put the call on mute straight away (so I can hear them, but they can't hear me) and waited for someone or something on the other end to speak.
There was silence and after 25 seconds, they hung up the call and called back straight away.
The second time they called, I did the same thing. Still silence from their side, no one said anything and that call lasted 36 seconds before they hung the call.