You actually signed up for the 7 day test drive for $0.01.  There is no recurring payment attached and therefore nothing to cancel.  After the 7 days are over, the trial credits will be removed from your account.  If you do not wish to use sku grid then you can either set the account on vacation mode in your general settings or you can purge all of your items out of the grid, by going to Advanced --> Purge All Items.  All of your items would then be deleted from sku grid.