Some more updates on this...
Bottom line - In my case, Samsung customer service was poor. Shah's was not a reliable dealer. Both Samsung and Shah's expect the customer to run behind them to avail service. My advice to all is to exercise caution when buying from Shah's or from Samsung.
Here's a detailed chronology of events that had happened...
30/3 - bought Samsung B450 42" plasma TV from Shah's, Anna Nagar, Chennai.
Next day - TV got delivered in the evening.
2nd Day - Complained to dealer about burn-in prob. (Detailed in 1st post)
4th day - Took pictures of TV showing burn-in and visited dealer. Dealer acknowledges issue and promises me a replacement within 3 days.
5th day to 44 days later - Kept calling dealer asking for replacement while being given a response like 'You'll surely get a replacement after we get new stocks. We'll get new stocks within a week.'
45 days later - Called dealer from a different number enquiring about C450. Was given a price of 44k. Called from my number and asked for a C450 replacement for my defective B450. Dealer tries evading the issue.
46 days later - Visited dealer for the 3rd time and enquired about my problem and the replacement promised. Dealer says C450 plasma was still not available and on the phone the attendant confused between C450 LCD and C450 plasma. Store manager talks to me and promises me a B450 or C450 replacement (yet again). Store manager shouts at employees for not raising a case with Samsung. I ask him politely why this must be reported to Samsung as it is an issue created at the dealer's side. Manager says everything must be reported to Samsung, even cases where the TV was broken in transit and reached customer in broken condition. I finally warn them that I'll wait for no more than a week and will not leave the store without getting a refund by next week.
47 days later - A manager from Shah's corporate office calls me and politely tells me that my replacement is guaranteed and I'll only have to wait till new stocks arrive. And he is not sure when new stocks will arrive as that is not under his control. Samsung customer service calls me and asks about the problem.
48 days later - A person from Samsung comes home and inspects the TV and confirms the burn in problem. He tell it can be easily rectified by repairing the panel. I insist I don't want repairs as I did not create the burn-in problem and that I want a replacement. He promises the TV will be surely replaced as and when new stocks arrive.
48-59 days - I keep waiting for replacement.
2 months later - A woman from Samsung calls me and tells me that I will be given a full refund because new stock won't arrive for the next 3 months. She confirms my name and initials and says a DD will be sent within a week.
2 months and 10 days later - No contact from either Samsung or the dealer. I try contacting the dealer and asking him about the refund. He says refund will come directly from Samsung and asks me to give him a day's time to update about the progress of the refund process.
Next 5 days - Dealer doesn't call back and update about progress. I try contacting Samsung customer care and enquire about refund progress. The CRM call centre guys have no idea what they're talking about and give a standard robotic reply - 'Your issue has been escalated and you will be contacted by our service manager.' And then no one calls back.
Today, after 2.5 months - I get frustrated with Samsung customer care's zero response and contact the dealer instead and for the first time, get angry and shout on phone. Dealer says Samsung will directly deal with the refund and gives me the personal mobile number of Samsung's service manager. I talk to Mr.Vijaykumar from Samsung and he tells me my refund has been approved and I should get my DD within 4-6 days and apologises for the delays as the process requires approval from 4 people and hence the delay. I ask him for an email from his official mail ID confirming the approval of my refund and he replies he doesn't have an official email ID! I ask him for an sms from his personal mobile confirming the refund approval. He first hesitates and asks me to wait, then agrees. After a reminder SMS from me, he finally sends an SMS saying 'Your DD will reach you in 4 days.'
Now, I am sitting at home staring at my defective Samsung B450 which is still sitting on my oversized TV stand occupying lots of floor space and obstructing my wall-mounted centre speaker, 2.5 months after I had complained about the burn-in problem.