I don't know if anyone has ran into NetSuite Defect #500869, but basically in some instances NetSuite will not allow you to delete customer credit cards and returns a referential integrity error. It's a U5 defect so it'll be 3-6 weeks until they fix it. I ended up writing a function based on their workaround to delete credit cards and thought someone here might need it / the logic behind it. You just send it a customer id and a credit card internal id.

good find