Front Seat Belt Buckle Assembly problems of the 2003 Dodge Grand Caravan

I purchased my 2003 Dodge Grand Caravan and took it into hall Dodge dealership in virginia beach va for routine maintenance and informed them that my passenger seat belt continuously unlocks itself and has to be checked regularly for security while driving. I took the vehicle in once again for a second time and reiterated that the seat belt was doing the same thing. They told me the vehicle was just over the warranty and would cost almost $300 to repair the seat belt. I told them it was a safety item and to check for recalls. The service guy told me that the bottom locking devise on the seat belt was inoperable and needed to be replaced. Please look into this matter as the seat belt is very unsafe.