Same as David, some Indian women with extremely bad voice quality tried to explain that my Windows machine was having security issues. When I requested her phone number she gave it to me then promptly hung up.
Just in case your not clear this is a SCAM

Had a call from some Indian women from "Lets Assist" regarding Windows Error messages. I strung her along for about 20 minutes and finally told her that her company was brilliant as I run an Apple Mac. She then told me to .... off. Nice!