Most (all?) subscriptions pre-pay for a defined subscription period and auto-renew when the subscription period expires. When you unsubscribe it stops the auto-renewal but the current subscription stays active until the prepaid subscription period runs out. Few, if any, will cancel immediately and refund the unused portion of your prepaid subscription.
This is all explained in the conditions you agreed to when you subscribed -- you know, all that stuff you agreed to without actually reading it.