Recently there has been a rash of phone call scams claiming to be from Microsoft. In most cases the callers have a heavy Pakistani / Indian accent. They are very persistent, calling back and asking why you hung up.
Microsoft will not call you except in a few extreme circumstances and then they will insist that you verify the call by calling a number at their web site. See: Microsoft phone scams and Online Privacy.
I have had reports of this both in the US and Europe. My local computer tech says he is seeing this way more frequently lately.
If you get such a call HANG UP! Repeatedly if you have to!
May you live in interesting times.
Rambling with Shug 