SELECT TN.*
FROM (SELECT TN2.ServiceID, TN2.CustomerID, TN2.AmountExGST, TN2.SupplierServiceCodeID,
 ((TN2.NumCalls * TN2.FlagFall) + (TN2.NumCalls * TN2.FixedCharge) +
 (TN2.Duration * TN2.InitialCharge)) AS "CalcAmtExGST"
FROM (SELECT TN1.*, 
 (CASE WHEN FixedCharge IS NULL THEN 0 ELSE FixedCharge END) AS "FixedCharge",
 (CASE WHEN FlagFall IS NULL THEN 0 ELSE FlagFall END) AS "FlagFall",
 (CASE WHEN Period1Charge IS NULL THEN 0 ELSE Period1Charge END) AS "InitialCharge"
FROM (SELECT ServiceID, CustomerID, Count(*) AS "NumCalls",
 Sum(CAST(Duration AS int)) AS "Duration",
 Sum(AmountExGST) AS "AmountExGST",
 SupplierServiceCodeID
FROM tTransaction
WHERE BatchID = 11111
 AND Duration IS NOT NULL
GROUP BY ServiceID, CustomerID, SupplierServiceCodeID) AS TN1
LEFT JOIN tAgreementTariffs ON TN1.SupplierServiceCodeID = tAgreementTariffs.SupplierServiceCodeID
LEFT JOIN tAgreement ON tAgreementTariffs.AgreementID = tAgreement.ID
WHERE tAgreement.BatchTypeID = 25
AND tAgreementTariffs.Active = 1
AND tAgreement.Active = 1) AS TN2) AS TN
WHERE TN.CalcAmtExGST > (1.1 * TN.AmountExGST)