Not sure whether it was a telemarketer or non profit but call was exactly as Warwick said above. The lack of a message sent of bells so I checked the number.

They leave a message using your name, and their first name, like it's a personal call. "Hi Warwick it's xxxx here, give me a call back when you have a moment" No mention at all about what it's about. Very annoying!

Very persistent and mysterious