There could be many possible reasons for this problem.
1) Charger or charger cable is not working properly, try different charger and charging cable.
2) The socket in which you're connecting your charger has many other load (specially different chargers) attached to it, This also cause Harmonics in power quality and cause touch issues while charging phone. Try different socket in your home/office to charge. Make sure only your phone charger is attached to that socket.
3) There could be some issue in power quality. Sometime there's non zero voltage in ground terminal in Pakistan specially in rainy season, that also cause same issue. Try charging your phone at some different location also.
4) Last possible issue could be a problem with your phone, because of fall and heavy drop, sometimes filtering capacitor get removed from main circuit board, or from touch digitiser. It also cause same issue. If you have tried different charger and charging location, then it must be problem with your phone itself.
As here in Pakistan no one do board level repairing, so only option for you is to keep using it as it is.. Or you may get it checked by some professional, maybe only digitiser is faulty and can be replaced easily.
