Certain Samsung smartphone models, such as the Galaxy S3, have the capability of blocking phone calls from unwanted numbers. There are a number of third-party apps for Android that give someone the ability to block private or unknown callers.
According to WonderHowTo, there are several ways to block either unknown callers or certain phone numbers on a Galaxy S3. In the Contacts app, there is a feature called "auto rejects list." The user can add any contact from her phone. This results in that person's calls going straight to voicemail. The auto reject settings are also accessed by going to Settings and choosing the Auto Reject Mode on many Samsung models, according to Radio Shack.
Several third-party Android apps, including Call Control, Call Blocker, Mr. Number, WhosCall and Calls Blacklist, give the user the ability to block phone calls from unknown sources.