Please try Concorde's First Class membership free for one month using the coupon code "firstmonthfree", which is available to all users.
Ok, didn't see it! =)
Is it mandatory to fill my CC details in order to subscribe with the promotion? (I don't really enjoy doing that...)
Yes, sorry, at the moment it is mandatory to add a credit card to sign up for a First Class account. I believe this is actually a limitation with my payments vendor, Stripe.