First you need to open commmand line and navigate to office installation directory.
If you installed the 64-bit version of Office 2016, move to the following folder: C:\Program Files\Microsoft Office\Office16
If you installed the 32-bit version of Office 2016, move to the following folder: C:\Program Files (x86)\Microsoft Office\Office16
Display the current licences
cscript ospp.vbs /dstatus
Remove the Licences
cscript ospp.vbs /unpkey:<last five characters of product key>
Now you need just restart PC and reactivate your office with your required key.
This should also work on the other versions of office. You just to need move to the correct instalation folder.