Xiaomi India — network issue in handset

Address:

110027

I am facing network issue in my 9 months old mi a1 set. Request you to replace the defective handset with the new one. I have contacted service center tegore garden but they are unable to help me. I have handled it very carefully and never used it in rain or extreme heat.
The mobile also not displaying incoming calls, i have to lock the mobile and then again unlock and then click on curren call to see the incoming call on my mobile display.