1) Go to:
www.whatsmyip.org
2) Write it down
3) Find your modem, not router, and unplug it and plug it back in
4) When internet works again, go back to
www.whatsmyip.org
5) If it's the same as the IP you had before, proceed to the next step.
6) Call your ISP, tell them you feel someone is trying to attack you through your IP address. Ask for a new IP.
7) If your ISP doesn't help, consider using a paid VPN service.
You can also try:
A) Asking your neighbors permission to use his WiFi.
B) Setting up a SSH service on you buddies computer, and tunneling your runescape traffic through that
C) Sending Jagex lots of money
D) Buying a VPS and tunneling your runescape traffic through that.