Cancelling a free trial does not grant a refund after it was charged. You need to cancel free trials at least 24 hours before the trial ends to avoid being charged.
If you do request a refund and it is approved, it will be posted to the same card used to make the purchase. If you had cancelled or removed that card, then you will get a credit note instead. A credit note may also be given to offset a charge that shows as pending and will later be removed. If the charge shows "pending" then the money has not actually been taken from your account yet and the credit note will prevent that from happening.