Mileage dropping

Caught VNS motors Plenty of Times dropping mileage on their vehicles,Went to view a Private sale bmw 3 series the car had 258000km on the clock at the time of viewing,The next day i seen the exact same car for sale at VNS with a fraction of the original mileage 155000km confronted them with it and they said they will contact the previous owner.The previous owner assured me that he sold the car to the at 258000km.Funny how almost all of their vehicles have between 155000km-180000km on the clock