Latency Variation

Hello, I have Xfinity for some time now, never had any issues. But yesterday I tried playing COD MWIII and I kept getting latency variation, I thought it was the servers of the game being a new game I know the servers are getting slammed. But none of my friends are having this issue. I called customer support. They sent a signal to restart my router, that did not work. I unplugged it, plugged it back in, that did not work. I even reinstalled my network drivers on my computer, nothing. Made sure everything is plugged in correctly. Really do not understand what this issue is, I have been researching online and there seems to be no fix for this issue.