Maruti Suzuki India — I am complaining about accidental car not repairing under insurance and open engine without asking me

My name is Hasmat Ali From Pallia Kalan Uttar Pradesh India 262902 My car is Ertiga Vehicle number is UP 31 CT 4854 commercial registered. My car got an accident and car was damaged hugely. They were repaired and modified the body and then they try to start car it didn’t. At that point they open car engine without informing me. They should inform the customer before open the car engine now they want me to pay for repairing and the car was just 90 days old. They are not repairing engine under the insurance coverage. They are keep denying to repair and not admitting their faults.