Sony ericsson Zylo
Display not working well after getting changed from service cente

I bought my zylo phone in Oct. After using it for 6 months its displayed did not worked well. When I gave my phone to service center they said that they have changed some hardware. After that phone display was working well. But now after using it for 6 months I am facing the same problem with display (when I open the slider display becomes blue and my phone stops working). I heard that there is some problem with the first lot of the handset. I request company to change my handset.