A big cloudy spot appears in the screen and an another one too but it is smaller. When i rotate my screen to watch pics then also it appears in the same position. I had given my phone to care before. I think they have damaged my phone at that place.
Sounds like there is a depression on the screen. In most cases an over zealous tech squeezing the screen to hard. I would send it back to the service place and request a replacement phone. Also take a picture of the phone since you got it back as evidence. At this point there is nothing you can do to release the depression.