Update:
Got my phone from the service center guys after 1 month. Updated with Black OS. But with new issues:
1. Mic not working.
2. Camera not working. It exits immediately after launch.
Went back to the service center to get it fixed and they tried the following:
1. OS reset. No luck.
2. Mic changed: Mic started working. But camera issue still present.
3. Tried with another A cover. Camera still not working.
4. Factory reset, amber update, black update: Cam still not working.
They have now sent the phone over to the main service center at Chennai. It would take another 10 days to get my phone back.
Really disappointed with Nokia service. They should have replaced my phone if they could not fix it.