I sent them a final message:
Based on your responses to previous messages, I doubt you will care. I've made the other 28,637 members of The Trading Card Database aware of your lack of customer service. I provided screenshots of all your message responses so they can see for themselves what to expect from you. Based on the responses to my post on The Trading Card Database, you already lost quite lot of customers and potential customers.
Someday my cards may double in value and then be worth half of what I paid for them.