FWIW
If you look good and hard, Microsoft has a link to a mobile phone option that you can use to activate the OS on a given machine during the activation process. (uses text message)

Faster than the regular phone activation method, more likely to succeed than other methods, and pretty easy to do. (in my experience)

The 'regular' phone method (phone call) is more likely to succeed than using the basic OS activation method in my experience, but the mobile phone (text) option has always seemed to just work. At least for me (W7,W8 and W10).

One of our IT guys showed me this (we have an IT division that works with some pretty large companies), so thought I'd mention/share.
Availability may be US based only, dunno.
Using this method, MS sends a text to your mobile phone with a link to copy/paste the code .. and I've had very good success this way. Including for activating Windows on other company's network machines (not MY personal/professional OS/license) but it still worked.
Of course I had a legit code for the given machine, but I was surprised it let me use my mobile phone multiple times for multiple machines. And seemed faster and less frustrating.

I do not work here, but the benefits are still awesome
Make your sound your own!