How do I Deal with this rumor?

Apparently, there has been a rumor going around that I hooked up with one certain individual. It is NOT true, but I fear it is going to keep spreading, and ruin my reputation. How do I stop it from spreading? How do I keep it from ruining my future school (and band camp) on-goings? How do I overcome the lies and just keep going? It is running me down, and I need some kind of fix. It is also summer, which would make it harder to destroy. Please Help!