CREATE TABLE services (service_id VARCHAR2, service_name VARCHAR2)
CREATE TABLE customers (customer_name VARCHAR2, customer_id VARCHAR2)
CREATE TABLE first_notification_of_loss (customer_id VARCHAR2, service_id VARCHAR2)

Find the names of customers who have used either the service 'Close a policy' or the service 'Upgrade a policy'.
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"
SELECT "t1"."customer_name" FROM "customers" "t1" JOIN "first_notification_of_loss" "t2" ON "t1"."customer_id" = "t2"."customer_id" JOIN "services" "t3" ON ("Close a policy" = "t3"."service_name" OR "Upgrade a policy" = "t3"."service_name") AND "t2"."service_id" = "t3"."service_id"