Deleted

You can delete a giveaway at any time before it ends.
Once it ends, you'll need the winner's permission to delete the giveaway- this is best done by having them leave a comment in the giveaway itself stating they approve of the deletion (otherwise, you'll need to provide a screenshot of the agreement). Without this, it's unlikely you'll be able to get a deletion.

As far as wait time goes, support appears to have been mostly inactive during the holidays. There are currently roughly 2500 pending support requests, not including user reports (which are typically addressed only after other tickets are cleared). As such, there may be a bit of a wait before your ticket will be able to be looked at. Tickets are addressed in the order they were submitted, so it's just a matter of them getting to it. Just be careful not to "bump" your ticket, as that will cause it to reset its queue time to the new comment- meaning all other currently active tickets will then be pushed ahead of yours in the response order.

I see only one opened giveaway. On the left side you find "Delete giveaway", click on it.