Norton anti virus scam?

I got a voicemail telling me that I would be charged $299 to renew my computer subscription unless I called back. I called the number and said I had no subscription. They claimed I have Norton on my Mac although I don't know it. In order to cancel they wanted me to go to my computer for something. At that point I hung up. I assume this is some kind of a scam and they were going to ask for information about my imac. Have you heard of this? It is a scam, right?