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"