sql query gives invalid column name

SELECT CAST(T1. [Free_Text]  as varchar(250)), CardCode, CardName, PymntGroup, SUM(Balance) BALANCE, SUM(A) FUTURE, SUM(B) '0-30', SUM(C) '31-60', SUM(D) '61-90', SUM(E) '91-120', SUM(F) '121+' FROM (
SELECT CAST(T1. [Free_Text]  as varchar(250)),T1.CardCode, T1.CardName, T2.[PymntGroup], T0.RefDate, T0.Ref1 'Document_Number',
     CASE  WHEN T0.TransType=13 THEN 'Invoice'
          WHEN T0.TransType=14 THEN 'Credit Note'
          WHEN T0.TransType=30 THEN 'Journal'
          WHEN T0.TransType=24 THEN 'Receipt'
          END AS 'Document_Type',
     T0.DueDate, (T0.Debit- T0.Credit) 'Balance'
     ,ISNULL((SELECT T0.Debit-T0.Credit WHERE DateDiff(day, T0.DueDate, getdate())<=-1),0) 'A'
     ,ISNULL((SELECT T0.Debit-T0.Credit WHERE DateDiff(day, T0.DueDate,getdate())>=0 and DateDiff(day, T0.DueDate,getdate())<=30),0) 'B'
     ,ISNULL((SELECT T0.Debit-T0.Credit WHERE DateDiff(day, T0.DueDate,getdate())>30 and DateDiff(day, T0.DueDate,getdate())<=60),0) 'C'
     ,ISNULL((SELECT T0.Debit-T0.Credit WHERE DateDiff(day, T0.DueDate,getdate())>60 and DateDiff(day, T0.DueDate,getdate())<=90),0) 'D'
     ,ISNULL((SELECT T0.Debit-T0.Credit WHERE DateDiff(day, T0.DueDate,getdate())>90 and DateDiff(day, T0.DueDate,getdate())<=120),0) 'E'
     ,ISNULL((SELECT T0.Debit-T0.Credit WHERE DateDiff(day, T0.DueDate,getdate())>=121),0) 'F'
FROM JDT1 T0 INNER JOIN OCRD T1 ON T0.ShortName = T1.CardCode
Left outer join  OCTG T2 On T1.GroupNum = T2.GroupNum
WHERE  T1.CardType = 'C' 
) T100
GROUP BY CARDCODE, CARDNAME, PymntGroup
ORDER BY CARDCODE