Help figuring out is_member_of

[sully02]

I have a snippet of code in a file that displays a message for those not in paid membership groups. The problem is, despite my attempts to code it so the paid members can't see it, they still see the message. Here's the conditional I'm currently using:

PHP Code:

if (!is_member_of($bbuserinfo, 18) OR !is_member_of($bbuserinfo, 19) OR !is_member_of($bbuserinfo, 20))
         {
                  //Code I don't want paying members to see
        } 


However, it's not working. Can anyone help me figure out what I'm doing wrong?