Certain features are only available with certain subscription plans. When you downgrade your account to a lower paid or free plan, you lose access to some features, and may even lose access to custom domains.
Links you've already created will continue to work as long as the domain's DNS settings point to Bitly. For complimentary domains, this connection will break after the complimentary domain expires. That expiration date and all the features that will change are listed on the downgrade confirmation screen when you downgrade your account.
To see which features are available on each plan, visit our pricing page. To learn how to change your plan, visit How do I change my Bitly subscription?