I have a customer with several lines who just added MLS6 phones. The MLS6 phones only show the first four lines. I tried programming auto line select for CO 1,2,3,4,5,6,7, but get a busy signal after lines 1-4 are busy. Is there a way to enable pool mode on this version? Is there a way to select a line that does not appear on your phone? I also tried line access 805, 806, and 807.