As mentioned above the problem is with dust under the trackball/pad.
In Faisalabad, go to katchery bazar and there will be repair shops on the right. Make sure to get the job done under their super vision since they are known to replace parts lol. I had a bad experience with my Nokia 5610, the repair guy managed to break the gloss black glass on the front... You can find diy guides online on iFixit website.