Godrej Locking Solutions & Systems — I am complaining about charge for under warranty product

I purchased 4 godrej door lock 3 month ago from local shop.one of lock now not functioning. I register a complain company by call.but they are demanding charge to repair the lock. My lock is under warranty for 1 year but they denied to repair it free of cost. They told me that as I installed lock from local carpainter so my warranty is void. But there is no such a point of their warrany card as well as local shop owner did not told me that installation only done by company technician. Company cheated people like this.So I demanding my warranty by company as lock under warranty.