Again, you're not providing enough information. What brand/model of phone system is it? Which applications are you installing that are failing to work? How are you comfiguring them?
You mention that you're not the PBX administrator (at least that's what I take away from the "not me" bit) so you're probably limited as to what you can accomplish here. Have you tried getting this person on board with your project? If you don't HAVE an in-house PBX admin and this is all being outsourced to a vendor, have you asked them?