Way to change voltage on cell phone charger?

So I got a PC fan and I hacked up an old cell phone charger that was only 6V. Is there a way to make it 12V? May sound like a dumb question, but I have no idea! It has 3 wires, red, black, and white. The PC fan also has red, white, and black. I matched up all three colors and it works and everything, but wanted to know if there is a way to give it more power...

nope, get a new adapter

Yea I figured that, but wanted to be 100% sure before I started hacking up another one!! Thanks russ0r!!