Subscriptions is where you're able to control everything you've signed up for, subscribed users, numbers and any add-ons. These are all items which will have a direct billing impact. From Subscriptions you're also able to cancel your service completely.
Subscriptions is not where you go to purchase additional users, numbers or add-ons, it is only for managing existing purchases.
Here you can quickly get a list based on subscription type and are offered the ability to remove or turn off specific features like International calling for many users at once.
If you have any Unassigned subscriptions they will be listed here. Each unassigned subscription is tied to a specific personal number that you may wish to keep. Any new users added will consume the next available unassigned subscription if one exists.
When removing any subscription or add-on, this will happen on the date of your renewal cycle. Until that date you will have the option to reverse your decision to remove that subscription or add-on without issue.