You must honor a recipient’s opt-out request within 10 business days. You can’t charge a fee, require the recipient to give you any personally identifying information beyond an email address, or make the recipient take any step other than sending a reply email or visiting a single page on an Internet website as a condition for honoring an opt-out request
OP could probably threaten a lawsuit and their practices will change quickly. That’s assuming the company does business in the US…
edit: just realized this is stubhub. this smells like a lawsuit waiting to happen