Block Calls on Any Phone
The following methods will work no matter what phone you have:
Google Voice
One of the best ways to block calls is to use Google Voice. If you don't have a Google Voice account and you live in the US, you can sign for one. Blocking calls with Google Voice is pretty simple: you have the option of sending them directly to voicemail, treating all their calls as spam, or blocking them entirely.
Here's how blocking works:
Log in to your Google Voice account.
Find the call you want to block (or the voicemail that resulted from it).
Select the check-box next to the call or voicemail.
Click the "more" link underneath the call.
Select "Block Caller."