Rear Seat Belt Buckle problems of the 2003 Ford F-350

The seat belt latch in the rear of my 2003 Ford f350 4dr quit working approx 1 year ago. The button stays in so it will not latch. I thought the seat belts had a longer warranty, so I wasn't to concerned to get it fixed right away. I got a recall notice from Ford for the cam position sensor (7. 3l diesel), so while it was in, I asked about the seatbelt. They said my warranty was out by less than 2 weeks and could not help me. I even contacted Ford customer service and again no help. I have an 88 chevy truck and a 95 GMC and have had no seatbelt issues. It seems to me that the belts should function properly for more than 5 years, and the fact that it went bad at around 4 years is even worse.