Hey alvinollet, where did you buy the phone. Unless I'm mistaken your Nokia warranty is only valid in the country you bought the phone. It sounds like your screen display cable (the ribbon cable) is broken, or at least something hardware to do with displaying the image. You might be able to fix the phone by getting a new screen yourself, but there's no guarantees... it's probably safer to take it to a local repair shop yourself and get it repaired but for a cost.
You say that sometimes the display comes back... are you able to get to the settings>about>reset menu to see if resetting the device to its factory state fixes the problem? This will erase your data on the phone, though.