Lenovo — Defective product and no support from service center also changed the motherboard without informing

Address:	New Delhi, Delhi, 110067
Website:	Lenovo

I bought lenovo k3 note and it doesn't catch network at all, when I visited the service center they said they need to update the software and kept the phone with them for one day. When I got my phone it was again not working, after few days I went to another service center and got my phone checked and service center people said that the motherboard of the phone has been changed as the IMEI no was different. When I visited the previous service center I got to know that it has been shifted to okhla from nehru place. I went to okhla and they first thry said they did not change it, when I told them about whole case they accepted that they have changed the motherboard. But did not help me. I went back to CP service center and they shared the contact no for regional manager of lenovo (Mr. Kuldeep Raina). After making 100s of call finally he picked up my call once and asked me to send all the details of my phone along with pick of the IMEI no. Post that I tried calling many but he didnt pick.
Please help else I have to file a case in Consumer.