When you call it, it instantly says "press 9 to be put on do not call list"
INSTABLOCK

I CAN NOT EMPHASIZE ENOUGH THAT PRESSING 9 [IN THIS EXAMPLE] WILL INFORM THEM THAT YOURS IS A WORKING NUMBER THAT THEY CAN NOW SELL TO OTHER IDIOTS!!!

You have to block them with your own method, not theirs. We are talking telescammers here, right?