SQL & PL/SQL

Hi all,

I am getting this weird error when trying to create a trigger. Basically it updates a different relationship table on INSERT or UPDATE.

The error I am getting is:
* PL/SQL: ORA-00904: "cid": invalid identifier*

SET SERVEROUTPUT ON
CREATE or REPLACE TRIGGER UPDATE_REL_TABLE 
	AFTER INSERT OR UPDATE ON XF_PROJECT_CODE
FOR EACH ROW 
DECLARE
	customer_count NUMBER;
	n_cid NUMBER;
BEGIN 
	-- CHECK if company exist
	SELECT COUNT(*) INTO customer_count FROM XF_CLIENTS WHERE UPPER(client_name) = UPPER(:NEW.company);
	
	CASE 
	WHEN customer_count > 0 THEN
		-- GET CUSTOMER ID
		select t.cid INTO n_cid FROM XF_CLIENTS t WHERE t.CLIENT_NAME = :NEW.company;   // ERROR HERE!!
		
		-- UPDATE relationship table
		INSERT INTO XF_CLIENT_CODE_R (PROJECT_CODE_ID, cid) VALUES (:NEW.project_code_id, n_cid);
	
	ELSE
		-- customer does not exist
		n_cid := XF_CLIENTS_SEQ.NEXTVAL;
		
		-- Create client
		INSERT INTO XF_CLIENTS(cid, client_name) VALUES(n_cid, :NEW.company);
			
		-- update relationship table
		INSERT INTO XF_CLIENT_CODE_R(project_code_id, XF_cid) VALUES (:NEW.project_code_id, n_cid);
		
	END CASE;
END; 
/
SHOW ERRORS;

The column exists and the data type (number) matches. Any help appreciated. bit at loss where I am going wrong.