WinSCP is a file transfer program – it doesn't have the concept of companies, nor is it in any way related to banking. So the question needs a lot more context to make sense. A lot more.
WinSCP is compatible with SFTP (SSH file transfer) servers, FTPS (FTP-TLS) servers, and the occassional SCP/FTP/WebDAV server. It is similar to e.g. FileZilla.
Possibly your organization already uses (runs or has access to) an SFTP or FTPS server which holds those banking files, and possibly has a user account per company (or at least a folder per company).
Beyond that, the task you described is specific to your organization's internal systems – not something that the general public can easily guess or help with.