Is there any setting option in my lg 5500 telus phone to remove the lines that appears on its screen?

When I bought this phone than there was not any line coming on the screen of my lg 5500 telus phone. But now when I changed the theme of the phone, then some lines are appearing on its screen. I have rested the previous theme, but still I am facing the same problem. So tell me that how can remove these lines from my phone screen?