Zephyr -Only 4 Users Need Zephyr, But We're Being Charged for 50 – What Are Our Options?

If we have 50 Jira  users and only 4 need to use Zephyr - how do I manage this so that we are only charged for 50 users? Paying for all 50 users means that the app becomes unaffordable This is pretty urgent. Please respond as soon as possible. Thanks