This has been posted several times. You should try doing a search next time.
Tools you need: Hex editor, FSdump, Wadmaker.
Dump your NAND.
The system channels are located in WII_FS\TITLE0010002\
You'll see several numbered folders and inside of each are two additional folders: DATA and CONTENT. The DATA folder stores all of the files for the channel. If you can't find the WADs for these channels online, keep these so you don't have to format.
If you open up the TMD file, you'll get the 4 digit Title ID for the channel.
Download the Internet Channel WAD.
Hex edit this title ID to the one for the channel you want to remove.
Use the WAD manager to first uninstall this channel, then install it.
Go to the Wii Channel Management and delete the channel. The ticket will stay, but the data will be removed. This prevents the channel from being re-installed when you insert a game with an update.
