Block calls by full number or by prefix / area code. Minimal Callblocker is a simple app that will automatically hang up on any phone number which matches a number in your block list. The incoming call is tested against the numbers in your blocklist to see if it starts with a matching number - this way you can block single numbers or a whole area code. There is also the option to block private numbers.
All blocked numbers are saved in a log file, they will also still show up in your phone app.