Refusal and Negligence in account of refund money to be disbursed

I purchased a Redmi Note 3 (worth Rs 11,999+ 600 Mi protect) from Mi India last year during the month of november. Due to some manufacturing defect,I returned my Smartphone back to Company’s address within the said amount of time. Now,it has been 3 months and i cant get my money refunded. Kindly note that There is very rare responce from company in this matter. Usually i call the customer support within 2-4 days but they have their usual way of saying the work will be done soon. Plz help me so that I can getmy money back