There is known issue in nokia lumia phones, please check following link.
https://google.co.in/search?q=known+issues+in+nokia+lumia+phone&oq=known+issues+in+nokia+lumia+phone&aqs=chrome.69i57j0.6343j0j9&sourceid=chrome&es_sm=122&ie=UTF-8
At last when I took my phone to Nokia service center, they said the touch panel has to be replaced and I’ve to pay them Rs 6500, despite of the fact that my phone is just 6 months old. The stupidest reply given by them was.
"Sir, your phone is physically damaged so warranty is lapsed." My phone had a small scratch in the hard plastic back cover, how is it related to the known issue with touch in Lumia phones? I’ve attached the picture of the so called physically damaged part of my phone.
Bottom line: terrible customer service, worthless warranty, phone has issues. Suggest avoiding Nokia at all costs!