From what I can gather based on your statement you are upset that you can't read all of the volumes of a Light Novel that you wanted to read.
That is unfortunate, but J-Novel Club is a subscription site where you are able to read the newest volume of a currently licensed series before it becomes an e-Book. Shortly after it is released as an e-Book it becomes unavailable to read.
Every month new series are put back on the subscription rotation as catch up titles, and that is certainly a way for new subscribers to make the most out of their subscription.
If you want to only read completed books, you can buy them from all major e-Book retail platforms, such as Amazon, Barns & Noble, KOBO, etc. If you want to read the latest volume of a series currently being translated before it hits virtual store shelves then the subscription is right for you, the subscription also allows you to purchase DRM -free copies of J-Novel Club Titles.
If you are not happy with your J-Novel Club Subscription you can email support@j-Novel.club and request a refund.
if you have any additional questions please let me know.