Malfunction notebook. Dell technican not able to resolve ?

I purchase a Dell Inspiron N4050 in May 2012. After a month, the machines malfunction with 'snowflakes' on the screen. This issue happen on and off but not often. However, for the past 1 month, it occur daily. Dell sent over your technican on Sep 28 and repaired on-site. The malfunction persist despite Dell technican informing they had change the necessary parts. I decided to request Dell to bring the notebook back to your technical center for full diagnosis and repaired on Oct 03. After 9 days, Dell technican returned my notebook stating there is no further issue on Oct 12 around 16:00 (video on this issue already sent on both occasion to Dell).)
Please look at the video i recorded on oct 12 at 16:21. IT IS STILL MALFUNTIONING. HOW CAN YOUR COMPANY SELL A MALFUNCTION NOTEBOOK ??
Service tag :  <ADMIN NOTE: Service tag removed per privacy policy> — in Kuala Lumpur

Dell technican had collected my notebook AGAIN on Oct 12, 18:10. I was informed by their customer service it will take 3 to 5 days to resolve.