Why are the phone activation keys cheaper?

Difference between online and phone activation key:

Microsoft offers several choices to activate your office (online or by phone) and the only difference between the online and phone activation key is that the phone activation key require to be activated by choosing “activation by phone” after the software is installed.

How to activate your Microsoft Office/Windows with a phone activation key?

While using a phone activation key to activate your Microsoft Office/Windows, an activation error will appears after the installation as in the screenshots below:

Before you start activation, make sure to install the office from the official link or from a direct link. Open excel or word or any other office app, then follow the phone activation instructions in one of the links below:

How to activate Office by Phone? Activation Guide

How to activate Windows by phone? Activation Guide