Summarize doesnt work on var table

Hi.
Please help me with following.
I have multiple tables (2 as example) from direct Power BI query - I need to consolidate them.
So my idea is to select data I need, UNION it and then summarize it by selected dimensions.
It works good with SUM, but I need to DISTINCTCOUNT one column and it doesnt accept it as reference.
I think it is taking it as measure, please suggest how to fix it?
Thank you!

Consolidated =

var Calls =  
        SELECTCOLUMNS(CallsRawSharePoint,
        "Site",                     "Global",
        "CalDate",                  related('Calendar'[Date].[Date]),
        "CallIDString",             0,
        "CallsForecasted",          0,
        "CallsOffered",             sum(CallsRawSharePoint[Total Offered Calls]),
        "CallsAnswered",            sum(CallsRawSharePoint[Total Answered Calls]),                  
        "CallsAnsweredSL",          sum(CallsRawSharePoint[Answered In SL]),
        "CallsAbandonedSL",         sum(CallsRawSharePoint[Abandoned In SL]),
        "NonCrit Score",            0,
        "QA Customer Critical",     0,
        "QA BusinessCrit Score",    0,              
        "ComplCrit Score",          0
)

var Quality =
        SELECTCOLUMNS(QA,
        "Site",                 related('Global Master List'[Global Site]),
        "CalDate",              related('Calendar'[Date].[Date]),
        "CallIDString",        [Call ID String],
        "CallsForecasted",      0,
        "CallsOffered",         0,
        "CallsAnswered",        0,                  
        "CallsAnsweredSL",      0,
        "CallsAbandonedSL",     0,
        "NonCrit Score",        [NonCrit Score %],
        "QA Customer Critical", [QA Customer Critical %] ,
        "QA BusinessCrit Score",[QA Business Critical %] ,              
        "ComplCrit Score",      [ComplCrit Score %]
)

var UnitedTable = union(Calls,Quality)

return SUMMARIZE(UnitedTable,
                [Site],
                [CalDate],
                "CallsOffered",     sum([CallsOffered]),
                "CallsAnswered"     sum([CallsAnswered]),
                "Monitorings Num",  DISTINCTCOUNT(CallIDString)
                )

 Last row doesnt work.