Stored Procedure Fails ORA-01036: illegal variable name/number

 if (DataBase == "MSSQL") // this gets executed if using MSSQL
        {
            SqlConnection conn = new SqlConnection("Data Source=SRVORDERS;Initial Catalog=ADLPRO2;User ID=OPTF;Password=#####;");
            SqlCommand cmd = new SqlCommand("OGEN.VALIDATE_PATIENT_NEW", conn);
            try
            {
                cmd.CommandType = CommandType.StoredProcedure;
                cmd.Parameters.AddWithValue("@LAST_NAME", LAST_NAME);
                cmd.Parameters.AddWithValue("@FIRST_NAME", FIRST_NAME);
                cmd.Parameters.AddWithValue("@DOB", DOB);
                cmd.Parameters.Add("@PAT_NUMBER", SqlDbType.Int);
                cmd.Parameters.Add("@FACILITY_KEY", SqlDbType.NChar, 4);
                cmd.Parameters["@PAT_NUMBER"].Direction = ParameterDirection.Output;
                cmd.Parameters["@FACILITY_KEY"].Direction = ParameterDirection.Output;
                cmd.Parameters.Add("@VALIDATED", SqlDbType.Int);
                cmd.Parameters["@VALIDATED"].Direction = ParameterDirection.Output;
                conn.Open();
                cmd.ExecuteNonQuery();
                Validated = Convert.ToInt32(cmd.Parameters["@VALIDATED"].Value);
                if (Validated > 0)
                {
                    patnumber = Convert.ToInt32(cmd.Parameters["@PAT_NUMBER"].Value);
                    FACILITY_KEY = (string)cmd.Parameters["@FACILITY_KEY"].Value;
                }
            }
            catch (Exception e)
            {
                conn.Close();
                using (StreamWriter sw = File.AppendText(log))
                {
                    sw.WriteLine(System.DateTime.Now + " OGEN.VALIDATE_PATIENT_NEW " + Success + "  PATNUM= " + patnumber + " Order No " + orderno);
                }
            }
        }

        else  //this gets executed if using Oracle 
        {
              OracleConnection conn = new OracleConnection("Data Source=SRVORDERS;User ID=OGEN;Password=#####;Unicode=True;");
              OracleCommand cmd = new OracleCommand("OGEN.VALIDATE_PATIENT_NEW", conn);
            try
            {
...

                cmd.Parameters.Add("@VALIDATED", OracleType.Int32);
                cmd.Parameters.Add("@PAT_NUMBER", OracleType.Int32);
                cmd.Parameters.Add("@FACILITY_KEY", OracleType.Char, 4);
           }
       } 

ALTER PROCEDURE [OGEN].[VALIDATE_PATIENT_NEW]
  (@VALIDATED INT OUTPUT,@LAST_NAME VARCHAR(30), @FIRST_NAME VARCHAR(30), @DOB datetime,@PAT_NUMBER INT OUTPUT,@FACILITY_KEY CHAR(4) OUTPUT)
AS
BEGIN
  SELECT @FACILITY_KEY = FACILITY_KEY,@PAT_NUMBER = PAT_NUMBER
  FROM OGEN.GEN_M_PATIENT_MAST WHERE UPPER(@LAST_NAME) = LAST_NAME AND UPPER(@FIRST_NAME) = FIRST_NAME AND @DOB = BIRTH_DATE
 SET @VALIDATED = @@ROWCOUNT
 RETURN
END

CREATE OR REPLACE PROCEDURE VALIDATE_PATIENT_NEW
(
  VALIDATED                  IN  OUT   int,
  LAST_NAME                  IN        VARCHAR2 DEFAULT NULL,
  FIRST_NAME                 IN        VARCHAR2 DEFAULT NULL,
  DOB                        IN        timestamp DEFAULT NULL,
  PAT_NUMBER                 IN  OUT   int,
  FACILITY_KEY               IN  OUT   CHAR
)
AS  
  BEGIN 
    BEGIN
      FOR REC IN ( SELECT
         FACILITY_KEY,
         PAT_NUMBER FROM  OGEN.GEN_M_PATIENT_MAST 
    WHERE   UPPER(VALIDATE_PATIENT_NEW.LAST_NAME)  = LAST_NAME
     AND  UPPER(VALIDATE_PATIENT_NEW.FIRST_NAME)  = FIRST_NAME
     AND  VALIDATE_PATIENT_NEW.DOB  = BIRTH_DATE
     )
      LOOP
        VALIDATE_PATIENT_NEW.FACILITY_KEY := REC.FACILITY_KEY;
        VALIDATE_PATIENT_NEW.PAT_NUMBER := REC.PAT_NUMBER;
      END LOOP;
    END;   
    VALIDATED  :=  SQL%ROWCOUNT; 
    RETURN;
  END;

cmd.ExecuteNonQuery();