Internet slows down for only one laptop after changing router and pack

Hello, My computer is Samsung 300V5A (just bought it few months ago). I live with a flatmate and we had a 5Mbit internet package. We decided to upgrade it to 30Mbit, and since then my internet connection is painfully slow, unlike my flatmate's laptop, which has top speed (30/1.5Mbit on speedtest.net). I would think the problem is with my laptop, but when I take it to other places, the speed...