The license you have is from your work? I'm asking because if it is, there is a slight chance that the administrator (or someone who has access to the O365 admin portal) set that the insider/beta builds to be available. If that is done, whoever tries to
install o365 within that organization gets the insider/beta builds instead of the normal o365 build.
In order to get rid of it someone should access the o365 admin portal, deactivate the usage of insider builds then you should unistall your office copy and re-download and install it. Then you will have fresh official build
If it's not that, dunno what else could be