Don't be a little noob. That will work in the case that they have a dynamic IP address, yes, but if they have a static IP address they will have to call their ISP as @Lemons said. Also, even if you have a dynamic IP address, sometimes your ISP will bind your IP address lease with your MAC address so that everytime you try to release your IP (by powering router on and off can be one way) you will continue to get the same IP address as long as your MAC address stays the same. In this case you will have to spoof your MAC address using software, and some routers have this feature.