Instructions For Activate The Windows 8.1 Pro by Phone :
1) Select the Start button, enter PC settings, and then select PC settings from the list of results.
2) Select Activate Windows, and then select Contact customer support for help.
3) You may be asked for an admin password or to confirm your choice.
4) Select your location from the drop-down list, and then select “Next”.
5) Then you will see Installation ID which is 63-digit numbers, now you can submit your Installation ID from our Get Confirmation ID page:
https://keysincaves.com/get-confirmation-id/
(Or you can call one of the numbers that are provided so you can get your Confirmation ID after submitting your Installation ID)
6) After receiving your Confirmation ID, you can enter your Confirmation ID, and your product will be activated.
If you need Windows 8.1 Pro product key you can purchase from HERE with best price!