Hide line key for voicemail number

I am using the VVX 410 UC Software Version 5.5.1.12442 and they are on a multi line hunt group. The hunt group has its own voicemail box and the phone has to be registered to the line to check the mail box. Is there a way to hide the line key for the voicemail line. I want it to show up on the message center but not on the line key.  

I noticed in the web gui there are 34 possilbe lines but when I register anything past line 12 they do not work.