Do you want to block a specific caller form leaving yo a voice mail, or do you want to block ALL voicemail? You can call customer service and have them remove voicemail from you account if you want to prevent all voicemails.
I am a consumer too and I sincerely understand your desire to block a specific number from calling you, rtaylor676. I can help. Please visit this link (http://spr.ly/6606Ee4Bu) for options to block numbers from calling you.
On a separate note (but not less important), are your current devices protected with Total Mobile Protection (http://spr.ly/6608Ee4Br)? If the answer is no, you can protect them now as we have open enrollment until 6/16/2019.