OnePlus India — No response from call centers and denial of service

Address: Thane, Maharashtra, 400607

I have a OnePlus One device purchased on 14th April 2015.
I have submitted the device at their andheri service center a month ago.
The service center asked me to pay for the replacement of motherboard because of which I called up the service center and my case had been escalated.
Mr Khan from their escalation team was supposed to call me. Every time I call the helpline they tell me that Mr Khan would call me in 24 hrs / 3 hours / Next Morning and do on. I have tried contacting them for 10-12 times and I haven't got a call back. My device is in service center since a month and I want to sue them for such pathetic service.
Never expected this kind of service and it has been really troublesome as I don't have my cellphone since a month now!
My case ID can be extracted from my mobile number : [protected]