general problems of the 2000 Nissan Frontier

Went into dealer to change passenger seat belt under life time warranty. Dealer said passenger seat belt was bad. Driver seat belt was replaced life time under warranty 5 months before. They said part seatbelt passenger was no longer in production and to call Nissan. I called Nissan and was given a case number. They told me they were searching for the part. Weeks go by with no official update but they changed the reps 2 times. The last Nissan representative diamond milan 615-725-7385 contacted me April 15th saying they could not find the part and would pay $800 for the trucks back. I questioned on why they would stop producing a lifetime warranty safety device passenger seat belt when it clearly could be a danger to rider in the passenger seat. Nissan had pictures of the truck and how great of condition it is. I told them I just wanted a seat belt fixed under the life time warranty not to give away my truck for $800 when which has line-x, nav and tow for work. I asked diamond milan how does that help me? she said that was kelly blue book was $800. When I looked it was $4k not $800. I asked why the seat belt mechanism can't be fixed. She said that "I" would have to find a dealer to do that. Would not answer my question on getting 2nd option. Any question after she would not answer.

Seat belt is fraying due to burr on shoulder belt guide. Still installed. Throttle cable is fraying/separating.