how to change ssh/sftp password if ssh shell is disabled and passwd command is disabled too

winscp says: “If your SSH server allows changing your account password, go to Session > Change Password to request that. “ – and it could change ssh/sftp password on server we use (but we not admin it).

But,

ssh user@server fails -> shell request failed on channel 0

and

ssh user@server passwd fails too -> exec request failed on channel 0

What are other possibilities to change password (from cmdline)?