FTP Server gets the wrong SSL certificate

Hello, I created a new FTP account under one of the websites I’m hosting, but when trying to connect, it gives out a self-signed certificate instead of the SSL certificate for the domain the website is using;

Also, I’ve noticed that the panel doesn’t have any instructions on how to connect to the FTP server, I could connect fine, but it would be nice if there were some explanation table I could just copy and paste to the customer.

What can I do about the FTP SSL certificate on port 21?