Everyone gets those pesky telemarketing calls from time to time. Who knows how they get your number. They may have acquired it from a contest you entered online, from a craigslist posting, or some online service that secretly sold your info to a 3rd party. There are also those people who continue to call after you have made it clear you no longer wish to hear from them.
Android now has the ability to block calls natively. The process for blocking numbers is similar but different depending on the brand of phone.
Motorola
-Open Contacts App
-Select contact to block
-tap menu
-select "all calls and voicemail"
Samsung
-Open Phone App
-Select More
-Go To Settings then Call Blocking
-Add Numbers to Block
LG
-Open Phone App
-Tap Menu
-Settings, Call Reject, Reject calls from
-Tap the plus icon and add numbers
Nexus
-Open Phone App
-Go to call log
-Select Number to block
-Tap menu
-Select add to reject list
HTC
-Open Phone App
-Go To Call History
-Long-press a number from the list
-Select Block contact or Block Caller
via DroidViews