Your release is so old, that you can't dial by extension number without dialing a digit first.
So what do you do? Your extensions are 100 through 120. From the main AA, 0 goes to another AA, without a greeting recorded, where 1 from that goes to another menu, again without a recording, where digit 0 transfers to 100, 1 transfers to 101, 2 to 102, etc.
From the top menu, 1 goes to another menu, where 0 transfers to 110, 1 to 111, and so.