Find me names of customers who have used the service "Close 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"
Find me names of customers who have also used 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" and t3.service_name = "Upgrade a policy"
Find me names of customers who have used either of the two services.
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"