Dialing '9' to be removed from their call list DOES NOT WORK. It's a ploy they use to determine if there is an actual, live person on the end of your line. Pressing any key during their call will result in your getting many more calls, not only from this caller but also from the other scammers to whom they will sell your phone number. The best advice is to screen calls based on CallerID - if you don't know who is calling, let them leave a voice message, but never give them any information, including pressing any keys.
Called my mobile a few minutes ago; did not recognize # so I let it roll to VM. VM recorded a few seconds of their spiel, but their system must be smart enough to realize it has not reached a live person, because it hung up.