So they sent it back to the service center for one month, when I got it back - the symptoms persisted, (and it has to see a "doctor") so I sent it back. It has stayed in the service center for almost 4 months, then I received a text from the store advising me to pick up my phone. Guess what, they just replaced my old phone with a new unit.
Before I get too excited about the replacement, I asked the attendant - WHAT IF, this unit has defect - she said they would use the date when I purchased the original unit as reference for the warranty. When I checked the receipt - it was dated 10/24/2009. Great. The warranty has just expired. Nevertheless, I am still thankful that they are accommodating enough to even accept my unit for repair. So now I am praying the unit is one of the best units ever produced for this model; and not just another unit they had received for repair and replacement.