Apparently you did. You have to trade with someone with the opposite version and get a Pokemon who knows Charge. Then take it to Opelucid City, more specifically the first building right of the Pokemon Center, upstairs (downstairs is the effort lady and upstairs is the radio guy). Talk to the radio guy and show him your traded Pokemon, then watch.

It's not really useful for you as a player, but it's a little bit of storyline that you can help unfold.