We have several ESI 24 key phones in our office. They have 5 phone lines connected but around a month ago, line 5 went dead on all of them. This wouldn't be a big deal, except that when we use speed dial, it dials on line 5 or if we press 9 for an outside line, it goes to line 5. Is is possible to program the phones to use line 4 for speed dial? Line 5 is not really necessary anyway, if I can just do away with it that would be fine. The issue is that most of the office relies on the speed dial and are unable to use it..