Able to purchase 18 character extension ticket but can use only 6

I bought 7 character extension ticket on store, there was no warning like you cant create more than 12 characters. So one of that 7th was completely useless. Steam says in game refunds on lost ark are not supported so go amazon. amazon support says go steam.
what kind of situation this is.
I want to refund that 1 extra ticket which is still on my product inventory.(in royal crystal)