Don't know who told you that, but there has never been hail basketball sized recorded anywhere in the world. I'm sure if there was, though, it would destroy a call in seconds and probably instantly kill an unprotected human being.
Matthew's right about the Vivian hailstone. The hailstone with the largest circumference (length of the stone all the way around) came in at 18.725 inches. That hailstone fell in Aurora, Nebraska. It previously held the record for the largest hail stone at 7 inches up until the Vivian stone.