What are the names of customers who have not taken a Mortage loan?
SELECT cust_name FROM customer EXCEPT SELECT T1.cust_name FROM customer AS T1 JOIN loan AS T2 ON T1.cust_id  =  T2.cust_id WHERE T2.loan_type  =  'Mortgages'
İpotek kredisi almayan müşterilerin adları nelerdir?