I have the galaxy S5 and had a robocall come in and say nothing so just hung up. Later went to recent call list and wrote number down and then chose the 3 bars at top of screen and select settings, call rejection, auto reject list. Select the + mark at top, it will come up with a screen that to can enter the phone #, then hit Save and it should work. Has for me now on two calls. Let me know if this works for you.