To manually add a number to your Send to voicemail list, select the Manage icon and select the Send to Voicemail tab.
Select the + button located at the top right-hand corner and manually enter the 10-digit number you would like to send to voicemail in the search box. Recent activity will appear as you type, selecting any number in the results will show a check mark over the icon, you may then select the “Send numbers to voicemail” button at the bottom of the screen to add one or multiple numbers that you may have selected.
If the page displays "No recent activity found. To send this number to voicemail, tap search and select it", follow those steps, and then press “Send numbers to voicemail” to add the number to the send to voicemail list.
If the number is listed on your Activity screen, select the number and from the expanded view, select “More” and then select the “Send to voicemail” icon. You may also select “More” and “See details” to view options to send the number to voicemail.