I am hearing that more than 25 numbers are needed. What I have found is if a number is blocked, that after about two months, they stop calling (maybe switch to a new number). Every six weeks or so, I delete all the numbers unless I see that they are still calling relentlessly. Just a few still are calling. I then start all over. I get almost no calls anymore. This works very well for me. Just an aside, I never give my phone number to anyone unless absolutely necessary. Stores and businesses have no reason to have my number other than to sell it or make annoying phone calls to me. If they want the sale, they do not need my number.