If you feel you were truly banned unlawfully, do what BDO players did: charge back. Hopefully you used a credit card/debit card. A simple call/visit to your bank branch will get your money back easily if you are in good standing with them. You will never be allowed to purchase the product again, but if your situation is true, I'm sure you are not wanting to. Keep in mind that YOU are the customer, and in most markets you have all the power.
A word of caution. You can get banned by the service you purchased from, Sony, Blizzard, and Microsoft have banned users accts for doing a chargeback.