Seat Belt Related Problems of the 2018 Volvo XC60

Seat Belt problem

The seatbelt warning only sounds for a few seconds then goes silent and never sounds again. This occurs at engine start, and also if I unbuckle the belt while moving. This happens to the driver and passenger belts. I took the car to the dealership where I purchased it, they had it overnight and the next day told me that this is the way is was designed. I called Volvo USA customer support and was told to take it to a dealer, and then began telling me that his Volvo ( unknown model or year) did not do this. The car has 1,300 miles.