Sure thing! After the technician has come by to install your Epic combo pack, you’ll receive an e-mail invitation from us for Shadow ("Your free Shadow account for high-level gaming"). Next, keeping this e-mail at hand, contact the Shadow help desk. They will ask you to forward that e-mail to them as proof and will then ensure that your chargeable subscription is converted into a free subscription!
You will keep all your data. The only things you won't be able to use anymore if you're a customer through Epic combo, are any chargeable "add-ons" you may already have purchased (e.g. the 1 TB storage).