How can I remove black ops server error of call of duty?

I installed Call of duty (Game) on my Computer. I was playing it online. It works accurately and without any error. But the next day, after the school, I try to connect my “Live Account” and play online but unfortunately, I got this message; The Call of Duty: Black Ops server is not available at this time.
Please try again later or visit call of duty web site for updates. Still it is not working. Is it Server problem? Kindly, tell me the solution to debug this error. Should I call Microsoft Support?
