billing error: when deleting a plan the customer still has to pay

error or feature.

A customer buys a plan and is billed 100,- then the reseller deletes the plan since it was a mistake, but the billing is still in place and has to be paid or canceled.

maybe its a good way to insure that the reseller can still claim the money for "work done"? But for me its an error. Maybe when deleting a plan there could be an option to also delete outstanding invoices related to this plan - I mean, if its not already concidered an error.