Real-time voice or video communication between users on mobile devices or computers
It is no longer possible to update billing address on Skype settings. This feature was recently disabled. Your billing address can now only be updated on your Microsoft account settings site.
https://learn.microsoft.com/en-us/answers/questions/5915612/how-to-add-new-billing-address
However, in order to update your billing address, you need first to set a country / region and language in your Microsoft account info.
https://learn.microsoft.com/en-us/answers/questions/5888305/wont-let-me-update-billing-address