Here are some tools that can help you remove an old version of Microsoft Office if you are having issues trying to install the new Office 365

Licence Removal Tool (LRT)

Office cleanup tool (OffScrub)

Access work or school

Click the windows button > your login picture > change account settings > access work or school > you should see the account you want to delete and click delete/remove

Credential Manager

Finally go and check out Credential Manager