We get so many call centres and what not that I do exactly the same thing, lift the receiver and hang up...sometimes it seems they call back 2-3 times and I just keep doing it till they call again but hang up before I can, seems like a joke to them.
Credit card calls, collection agencies ( when we never buy anything on time--pay cash or I don't buy) so it seems ridiculous but it seems this is the latest thing.
They even call on the cell phones now so I keep mine off unless going out.