Received call from this number, when called back the number was disconnected

I picked up the phone to shut it up, not to speak - I never answer calls from unknown numbers - and heard a man with a foreign accent saying "hello". The background noise sounded like that of a call centre, i.e. a scam factory, with foreign-accented people talking. (I left the line open for the next hour in the hope that it would stop them using it for calls, though that may not work these days.)
Lowlife scammers, without a doubt.