It works as it is supposed to! It can't protect you from illegal callers though. Consider maybe getting a call blocking device or phone.. You can google them and many are around $60.00 or so.
I got the same call yesterday. The caller hesitated on what he was going to say, then said he was from Lee County Sheriffs department. He was looking for donations. I told him not at this time. I looked up the number and found it to be some florist shop. Apparently illegitimate call. Apparent scam attempt!