Xaomi India - New phone not working

I ordered a phone Redmi ** prime from Xaomi India's official website mi.com. But the phone did not work as expected. It has some defects. Person on the other side is not able to hear anything. After facing the problem for * week I visited their authorized service center in Mathura ****** in first week of November, where they kept my phone for * days, and told that they have replaced mic. Even after that the problem was not resolved. I visited again yesterday on *th Nov, and I was suggested by the service center to replace SIM. I did that as well but no use. It seems that my money has gone waste. I have not got my money's worth. I seek refund of the entire amount, as I am not ready to accept a mobile handset which has manufacturing defect.