You can't cancel a bid once it's been placed. You either win the item or have the gold returned if someone outbids out. Removing an item from your watchlist does not cancel the bid.
If your trying to say that the gold still does not return to you when you get outbid then that would be a cause to raise a ticket via the help center. Although it's best to allow 24-48 hours first for the gold return to allow for any marketplace lag that may be occuring.