BROKEN NAVIGATION AND RADIO SYSTEM BREAKS LESS THAN A WEEK AFTER BUYING CAR

I bought my BMW last year and when after having the car for less than a week the Navigator and radio stopped working. Reported it and was told it would be fixed. After numerous calls the one part was fixed and when the costing came to complete the job the manager Anton and the owner refused to have it fixed saying it's too costly and this was after they accepted it was faulty and no fault of ours they refused to pay. A year later the Navigation system is still broken and after many encounters with Anton he now refuses to have it fixed. Totally disgusted as you expect to drive out with a reputable car and when you are promised it will be fixed especially as it broke less than a week after purchasing car and then being told it will be fixed utterly disgusted by this lack of morality.