I unwittingly took a free trail and I was charged for it today although I have not used it, can I request for a refund?

You'll need to cancel it first. Free trials will normally renew into paid subscriptions if not cancelled at least 24 hours before they are set to renew. Follow the steps here to cancel it: link-> How to cancel a subscription from Apple - Apple Support

Once you have correctly cancelled the subscription, then use there "contact Apple Support" link in the support article you posted from to contact Apple support and request a refund. Note that Apple is under no obligation to grant you one, but you can still try regardless and they are usually nice enough to grant one.