I have a customer that has only 50 phones installed and I just installed a Third PRI on there system. That gives them a total of 69 lines. They are still getting no free lines sometimes when calling out. Why would this be happening? I have tested all three PRI's and they are all working. They are all in pri group A. Is there something that would keep them from rolling to the next PRI when all lines are busy on the third pri?