Rear Seat Belt Buckle problems of the 2001 Nissan Quest

My middle drivers seat belt clip has broken. About 3 months ago the sleeve it is in started to slip and come loose. Until it finally came off and feel apart. I went to the dealer, at first they told me it was not under warranty then when I told him it had a lifetime warranty he checked on it and scheduled me with a service appointment in a week. When I brought it in for service, I was told they needed to order a part and it would take a week or so. It has now been 16 days and I have not been told the part is in. When I called they put me to parts, but no one answered after 5 minutes. I called them back and did not get any answer from the service department. No one seems concerned that my Mini van, which is used to haul children, does not have a working seat belt.