We do support adding additional information for a subscription using “provisioning attributes” that you can define in the price plan and then add customer/subscription specific values at the time of order. For example, CircuitID could be one of the attributes in the price plans that you need to capture the information for. You need to change your invoice template to use this attribute value to print on invoice along with other details.
After you modify the plan, you need to edit the existing subscriptions of this plan to enter appropriate values. It is recommended that you test the setup in a sandbox environment before doing it on production as some of the changes you do may be irreversible