Tata Motor - Car gear issue and tata motor not able to resolve

I have recently purchased a new tata nexon facelift in Oct**** but I noticed a gear problem within ** days and reported the issue to tata customer care. They have taken my car more than * times and told me again and again that the issue is resolved. But this issue is still coming on the road.. car is shifting gear automatically since it is a manual car. This is the concern of safety and may lead to any accident but tata motor is not taking my issue seriously. I am tired of complaining again and again. I just want my refund of the car as the issue is not resolved by the company.