Poor service

We upgraded a MTN contract and took a laptop - HP core i3. In the booklet it is indicated that it comes with Windows 10 and on my invoice it is indicated that Windows 11 is included. I tried to open Microsoft Word but it keeps asking for the activation code. I went to the store where we did the upgrade and they then informed me that I must buy it separately. If that is the case, why did they include it on my invoice and why did they not inform me that I must buy it separately?? Ig they did inform us we would not have done the upgrade