hack attack

I received a message that my computer was being attacked and I had to call Microsoft to get help with it.  I could not get off the screen and the message said I should not shut down.  I called the number and was successful on the third try.  The person said he needed to access my computer.  I said how did I know he wasn't accessing my info and he said it was a software problem, not a computer problem and so I allowed him access.  I asked why webroot had not picked up the problem and said it was a campi.  He then showed me the definition.  He then said Microsoft could fix my problem and it would take about 2 hours for the technicians to fix it.  I told him I would rather take it in myself.  Was this a new kind of scam?  Should I stop using my computer until it is fixed by someone?  Please advise.  Thank you.