Hyundai — defective gearbox in new hyundai creta

I bought new hyundai creta from punjab hyundai gandhinagar in dec 2016. After 3 months the third and fifth gear of the vehicle developed a problem. It used to get back to neutral while driving without the clutch being applied and i saved a near accident while travelling to pune coz of this. I sent the vehicle to a hyundai service station in nashik and addressed a mail to hyundai complaint cell. The vehicle was repaired citing some oil leakage from gearbox but now after two months the same problem has started again and it increases day by day. I wrote to hyundai again but no response from them. A gearbox problem in a new vehicle is not acceptable which has already caused me a lot of problem. I don't consider repairing the vehicle every month as an option. I request your kind intervention in the matter.
Regards
Major devendra singh maldhya
Veh - gj 18bf6252
Contact no [protected]
[protected]@gmail.com