Calculate Distinct Count for Customer exclude Customer Name consist of "GOL -"

You can create a DAX measure as follows:

Omni_No. of Customers = 
CALCULATE(
    DISTINCTCOUNT('Omni Sales Data'[Customer Code]),
    FILTER(
        ALL('Omni Sales Data'),
        LEFT('Omni Sales Data'[Customer Name] , 3) <> "GOL"
    )
)

This measure calculates the distinct customer code, excluding customers with "GOL" prefix. Here is the  solution screenshot:

As you can see, I have total 6 disticnt customers (ID is unique), but, 4 customers without the "GOL" prefix (as expected). Let me know if this solved your issue. 

Best Regards,
Udit

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