I used OData Test Service. Created new report with Telerik Reprot Designer R3-2019, added Web service datasource. I set Service URL this value: https://services.odata.org/V3/Northwind/Northwind.svc/Customers('DUMON')
And in second step I added one parameter, name: $select, type: Query, Value: CompanyName, Design-Time Value: CompanyName
Next, if you click on Download button, it shows error(400), see on the attached picture.
The question is how should we use odata request with $select (or $expand) operator?