Hiya on android will block calls from known spam numbers, or you can set it to allow the calls but flag them as known spam or telemarketers. It also supports blocking calls based on what the number starts with. So if you have a non local number, and spammers are spoofing a local number it is easy to block them without missing important calls. Lastly, how many calls do you get that are important, but not important enough that they would leave a voicemail?