the touchscreen does not work

My parents bought me in august iphone 5s gold in new york so its practically new but since then, it has not worked properly. Every time i want to unlock it, vertical lines appear on the screen so it is impossible for me to use it. The problem has not started after a fall, it just start happening one day from another and it had worsened with time. I have not got warranty, but considering its a technical issue, i think i should have a solution. Thank you.