If you subscribed before we changed the pricing plan from subscription to unlocking, you probably have noticed that you only have access to the free usage of it and we apologize about the situation.
There is only one way to get back on track. YOU MUST CLAIM A REFUND to the Appstore, download the last App on the store and go through the buying process again.
Here is the Apple procedure to claim a refund : Request a refund for apps or content you've bought from Apple – Apple Support (UK)