"Blocked" calls are also normally just diverted to voicemail. To prevent blocked callers from reaching your voicemail, set that conditional call forward to an invalid number, ie:
Also go into text messaging app to block the person from sending you text messaging apps. If that person has sent you text mesages, hold down on the person's name in the conversation list and use the block contact feature.
Go to your call log and hold your finger down on the person's number you want to block (if you have a smartphone but not all phones are the same) and you should get a bunch of options like add contact, etc and one is block.
If that don't work for you let us know what model of phone you have.
On your phone app screen, search for settings, then under settings there should be a section titled Blocked Numbers, or something to that effect. Click to enter that option and add the phone number to be blocked.
