Question: Find the names of customers who have used either the service "Close a policy" or the service "Upgrade a policy".
SQL: 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"