SSRS Report returning old data
When a report is first run in Visual Studio, it creates a cache of the data that is used for all subsequent executions, as long as you don't change parameters. You can refresh the data by either changing parameters, or deleting this cache of the data. 

To do so, navigate to your solution file and find the file for the report like YourReport.rdl.data and delete that. The next time you preview your report, it will query the database for the fresh data.