The signed contract says nothing about copyright transfer though I've heard by default your work belongs to you until you explicitly transfer rights. Even if t

The signed contract says nothing about copyright transfer though I've heard by default your work belongs to you until you explicitly transfer rights. Even if the contract did say something about copyright transfer (as it probably should), they don't receive those rights until they pay you. You absolutely have the right to shut them down. IANAL, though. You should see one if it has been more than 90 days since you delivered the work.