Shoutbox

These are the keys to press. It will open a shortcut when you start entering it, but keep entering the rest of the code and it will work.

right, star, left, left, star, left, star

There is nothing useful in there though, perhaps the coolest thing is the screen test pattern.

The message limit on your phone is set because otherwise the phone cant handle a huge amount of messages. The K750 has been hacked to raise the message limit, but opening folders takes much longer, and having too many messages will just crash the phone. I don't know of such a hack for K300 anyway.