Got my HTC desire 816DS repaired from HTC service center(Kohinoor city, Kurla) after 12 days. As per them, motherboard was found faulty and replaced. Phone was in warranty, so repaired free of charge. Now everything is working fine. Thanks for suggestions from all members.
Saw lot of people with complain in HTC desire 820 model(call/Battery/hang). So people desirous of buying 820, please be careful.