Dear Sirs,I use dot instead of comma to separate the thousands in my country. In Excel from my Office 365 Essentials I could not find how to change this default. I can only activate or deactivate the comma for thousands.
You could try checking your system settings if you have admin rights - which you may not be able to change if controlled by your business.
See attached picture...
I guess for Office 365 Business Essentials there are only Web applications (Excel Online), if so that's tenant admin shall change locale for OneDrive.