Which customers have used the service named "Close a policy" or "Upgrade a policy"? Give me the customer names.
SELECT t1.customer_name FROM customers AS t1 JOIN first_notification_of_loss AS t2 ON t1.customer_id  =  t2.customer_id JOIN services AS t3 ON t2.service_id  =  t3.service_id WHERE t3.service_name  =  "Close a policy" OR t3.service_name  =  "Upgrade a policy"
customers who have used the service refers to JOIN on customers, first_notification_of_loss, and services tables; service named Close a policy or Upgrade a policy refers to WHERE service_name = 'Close a policy' OR service_name = 'Upgrade a policy'; customer names refer to SELECT customer_name;