I received same call from same guy yesterday 1/22/2015. The caller ID indicated 407-555-0127 Dir Assist FL. I asked him which company he represented and he told me Windows Security Tech Department. I also asked him his office number and his office location. He replied 408-242-3315 in southern California. He asked me to go to my PC so he could fix my Windows. I asked him which window? back-door window or front-door window? He lost patience and started asking me 'do you know window?'. I told him I am using Apple computer not Windows. Then I asked him 'do you know Apple?' and he replied no. Finally I asked him to remove my name from his list, because I am not window user at all. Very annoyed.
They are using a switch number so you can't block them. I know that Microsoft doesn't call you about windows issues for a problem unless you ask for them to call you or they'd have to practically call everyone in the united states which is a waist of resources.
My wife got a call that went to voice mail. The caller was a woman with a thick British accent. She was calling about some kind of glitch in the federal tax system that could result in being charged with tax fraud, and if Mrs. wanted to avoid being arrested by federal authorities, she needed to call that number right away to get everything straightened out. Needless to say, we deleted the message and blocked the number.