As stated in our Terms of Service "Once you cancel you won’t be charged again, but you are responsible for whatever charges have already been incurred for the current billing period.". These terms apply to your account.
As far as the 30-day trial goes, the Terms of Service clearly state "in some cases", meaning special discounts or promotions. And it only applies to Premium account. Since you have a Featured User account and your purchase was not part of any promotion or special discount the case of the 30-day trial does not apply here.
Your Featured User campaign has run its course and you have gained followers through it. You will therefore, and per the terms stated in our ToS, not receive a refund on your payment.