SSRS report not displaying data in correct order

Question

Guys,
I have a SSRS 2012 report not displaying returned records from SQL in the correct order.  Running the stored procedure in SSMS and supplying the parameter values returns the data correctly and running Query Designer in SSRS using the stored procedure
on the dataset in question, likewise returns the data correctly.  Only when I run the actual report does the data display incorrectly(always last name order).  I've done similar reporting using very similar stored procedures and I've never had this
problem.  Below is the stored procedure.  "@SortBy" is the parameter with the sorting value. 1=Due Date; 2=Denial Amt and 3=Last name and is passed by SSRS to SQL.  Wish I could supply screen shots.  
Thanks for any help,
Dave
ALTER PROCEDURE [dbo].[RAC_PT_List]
@Level as int,
@SortBy as int,
@PTLName as varchar(30) = NULL,
@User as varchar(10) = NULL
AS
SELECT pat.headerID,
pat.PT_LName + ', ' + pat.PT_FName AS PTName,
pat.PT_AcctNo,
rco.RCO_CLMREF,
rco.RCO_AppealLevel,
rco.RCO_LevelNo,
rco.RCO_AuditorStatus,
let.LET_DEN_DueDate,
CONVERT(varchar(12),let.LET_DEN_DueDate) as DueDate,
let.LET_DEN_Dollars,
let.userID
FROM Master_PT_List pat
INNER JOIN Master_RCO_Work rco on RCO.PT_headerID = pat.headerID
INNER JOIN Master_Letters let on LET.PT_headerID = pat.headerID
WHERE (@PTLName IS NULL OR(pat.PT_LName LIKE + '%' + @PTLName + '%'))
AND (rco.RCO_LevelNo = @Level)
AND (let.userID = @User)
--AND (rco.RCO_AuditorStatus <> 'Closed' and rco.RCO_AdminStatus <> 'Closed')
ORDER BY 
CASE WHEN @SortBy = '1' THEN LET_DEN_DueDate
END
DESC,
CASE WHEN @SortBy = '2' THEN let.LET_DEN_Dollars
END
DESC,
CASE WHEN @SortBy = '3' THEN pat.PT_LName
END

Answer 1

Hi DaveMac1960,
According to your description, when you render data in report, you find it always shows the data with unexpected order. Right?
In Reporting Services, if we don't set any sorting in tablix, it will order the data as your query in SSMS or Query Builder. In some scenario, for example, we add parent group for data rows, it will have the rows sort by the group on data field by default,
and the "order by" in your query will be ignored. So please check the Sorting tab in Tablix Properties, in this scenario, we suggest you delete any sorting in the Sorting tab so that the "Order By" clause can work.
Reference:
Sort Data in a Data Region (Report Builder and SSRS)
If you have any question, please feel free to ask.
Best Regards,
Simon Hou