Mivi — Not returning the defective product I sent for repair

I bought mivi duopods m20 from Flipkart, after few months the duopods started malfunctioning so I contacted mivi customer care through email and they asked me to send the product for repair. I sent the product through their courier to Hyderabad and they confirmed that they received the product. After that I tried to contact them for update but they stopped replying, I waited for more than 2 weeks but still got no reply. They have my product and are not returning it. I saw many others had the same complaint. Please help me get the product back.