Lenovo - mobile softwae crashed

I am facing network issue from last three months. Lot of time visited Lenovo Service centre, Jamnagar location. Finally they have given me corrupted phone and they replied that we can't anything. Detailed history is attached here.
*. **th June I visited service center for Network issue, They have formatted and return back to me.
*. I visited on *th July for same issue, and came to know that mother board hard ware issue after *days they have replaced mother board and return back to me.
*. Still same network issue is persisting and always system itself rebooting. I visited again for Lenovo service Centre, again they have formatted and return back to me.
*. Still rebooting issue is not solved again I visited *st Aug. Finally they have given me non working phone. Finally they said in next update issue will resolve.
send mail to customer service, reply awaiting from Lenovo customer care.