Hisense Warranty passing the buck between Hisense and OK Furniture

My mother bought tv and it has strips took it to ok job no *** and technician says the screen has cricked but it was handed in the store without the crick, phoned the store they say technician said is the internal crick. When I call Hisense they say is not an internal crick is a crick but the store says the is no crick .I need a way forward because this TV is under warranty.