Couchdrop SFTP/FTP provides you the ability to turn your cloud storage (Azure, S3, OneDrive, etc.) into an SFTP or FTP server. All you need to do is connect your storage, create as many users as you need with permissions and you are good to go!
Before starting, you will require a Couchdrop account and a linked cloud storage provider.
Once you have an account, link your desired SFTP/FTP storage
Below we are using a BASH terminal, however Couchdrop works with any SFTP/FTP compliant software including the likes of FileZilla, CyberDuck, or applications that use SFTP as a backup method (3CX).
Start your interactive SFTP session using 'sftp <username>@sftp.couchdrop.io' 
To list the files currently in your endpoint use the standard Linux 'ls' command, to change to a sub-directory then 'cd <directory_name>' will take you to the nested directory
To upload files to your current SFTP cloud storage directory then 'put' will be the syntax used, and 'get' will be used to download files from your current SFTP session.