Is there a system in place that allows customers to Upgrade

Is there a system in place that allows customers to Upgrade their subscription? In other order words, I have single video access for $10, and All Video access for $30. At some point in time if they choose to upgrade to All Video access, right now I assume it will change them $30 and make them members of both subscriptions. Instead I would just want them to be a member of the All-Videos subscription and only be changed $20 for it.

Thank you.