Running Total based on Dimension level

Hello,

     I am trying to get the Running total based on ServiceID But getting an error. Below is my table data . I

Group     Service ID     Amount

   A               1                $2

   A               4                $1

   A               2                $3

   B               2                $1

   B               6                $4

When i try to create Rank based on the below dax getting an error "A single value for column ' Service ID ' in table 'Sampledata' cannot be determined. This can happen when a measure formula refers to a column that contains many values without specifying an aggregation such as min, max, count, or sum to get a single result"

Rank = RANKX(SampleData,SampleData[Service ID],,ASC,Dense)

for the Running total i am using below dax , But the Earlier function does not recognise the any column from the table.

RunningTotal =
CALCULATE (
    SUM ( SampleData[Amount] ),
    ALLEXCEPT ( SampleData, SampleData[Group] ),
    SampleData[Rank] <= EARLIER ( SampleData[Rank] )
)

Please help me know , what went wriong here. ? 

TIA

Midhun