Support is available regardless if your a subscriber or not. Currently the phone lines are down till further notice so you can email support@swtor.com if you need assistance. Just include your character name, server and Display Name.
As for the issue at hand, are you currently using a 7-day referral? If not and your not a subscriber is the item you tried to use still in your inventory? If so check your character window, go to companions and see if you can add a customization to them or if it's locked.
If it is still locked and your not able to use the item, email support at the email above.
