Well, the US seems to think that their rules are to be applied globally, especially when it's about audio/video material...

Just answer the phone and listen to them.

"I'm [name] from [name] and bla bla bla..."
After a while they will go "Hello? Hello? can you hear me?" and after a pause they'll hang up.
But because the number is not a sale/no sale, it'll come back in their loop, and they will call again.
Just repeat this, and try not to laugh at their distress.

I got the floor manager on the phone the 4th time. She told me I could just have said that I wasn't interested. I replied that that wasn't as much fun as this.