2500 Silveraido wont accelerate past 98

2015 Silverado almost got me killed because I cannot accelerate past 98 MPH have called GM several times and have gotten runaround dealership says they cannot do anything I must call GM. Maybe time to get a lawyer involved clear case of being mislead almost causing major freeway accident had I not gone out through meridian. $ 50,000.00 and the truck wont pass 98 and GM wont solve issues and respond in a timely manner, have been calling for the last 2 weeks and only owned the truck for 3-weeks