Xiaomi India — No response of service center

Address:

Kolkata, West Bengal, 700020

Sir,
My phone was submitted to service center on 17/4/16, and till date there is no response from there side.
I have made a complain to there customer service but found n o response, every time i visite there store they give an excuse date"till now aapka phone thik nai hua, wait kaijye ho jayega".
The service center is harassing me by calling me after a particular time and then denying.
Please help me out asap.