Caller: Supposedly NBN company!

A mobile number rings my landline apparently calling from NBN Co, but couldn't tell me which internet provider I used, just wanted to know about what devices I had connected to my modem. I anticipated a "we'll just install a security device on your phone for now" request to follow, so I hung up (politely, I'm nice) and they have not called back...so whatever problem it supposedly was must have sorted itself out!