Storing the info as plain text in the cookie, shows that they don't really know what they are doing. To think, not even popular free forum scripts do that. I don't think they really know what hashing is. That is why they can display the last few characters of the password in the logs. Seeing that a good hash, is supposed to be one-way, but now they are accessing parts of it. This shows that they simply store the password as plaintext or they encrypt everything with the same key. So if their db got exploited and their servers, the key would be found and everyone's login details will be gone as well.
A lot of free open source scripts for forums and ecommerce use salted hashtags nowadays. It is shocking that an ISP (like WebAfrica) can't do the same.
For the webafrica representative that sees nothing wrong in the plaintext cookie. You are supposed to put in a unique code string, that identifies the user. There are various ways you can do it, but just putting in the username and password is pathetic. And you need to clean up these strings after some time. Since it is a cookie, so it is supposed to be temporary.
With WA, the usernames are really short, and they all follow the same format. So its super easy to guess a different user's username. Atleast some of the other ISPs only use the email for logins.