you need to speak with the person that banned you from the channel.
mIRC do not control what is happening on the different chat networks, mIRC is only a chat client that allow you to access the chat servers.
send a message to the person who banned you, or as a friend check who is in the channel and find out who is channel operator (person with an @ infront of their nickname) and then send them a message asking what you did wrong and kindly ask if you can get unbanned from their channel.
good luck.
