I received a single call, picked up, and they promptly disconnected. Utterly pointless!

I received a call that rang once and then abruptly ended. Just a minute later, the same number called again. I picked up, but all that greeted me was silence. Quite peculiar, to say the least.

Received a single ring before they abruptly disconnected.

Received a single call then they disconnected. No way I'll be returning that call!

I picked up the call, but they promptly disconnected without saying a word.