I think that if they are just blatantly changi their terms and conditions in order to avoid paying the promo codes that they issued before, they should really be ashamed of themselves. Just because bitcoin went up, doesn't mean that their duty to fulfill their previous promises can be void.

Plus, these kind of money is probably absolutely miniscule in terms of their trading volume. They can obviously afford to pay for this.

You've gotten verified for this, and they should allow you to claim whatever balance you have with them, whether or not you got it from a coupon for free or not. They haven't stated this before you signed up and redeemed the coupon code either as it seems.