Left a recording (you cannot call it a message) on my machine of people in a call centre talking amongst themselves.  The sound is garbled, as if the operator had their hand on the microphone, but they were speaking North American (based on the slang phrases heard) English, so this is a home-grown rather than foreign scam.  Recording ended with a male voice making a sound of surprise (probably discovering that a call had been connected) and a hang-up.  Could not tell what scam they were trying to pull.

Call 2 times in 2 hours never left a message

I have received multiple calls daily and several times during the week from this number.  No message is ever left.