Hi, @Syndicate_Admin
Go to the Model view in Power BI Desktop. Drag and drop the column from the table onto the column in the table to create a relationship, make sure the relationship is set to a one-to-many (1:*) cardinality, with the table on the "one" side and the table on the "many" side. This setup assumes that each company can have more than one contact.
On the report canvas, add a slicer visual and set its data fields to columns in the table. Add another table visual to the canvas and include the columns that appear from the table. The slicer will now control the table visual to show only the contacts related to the selected company number.
You can check the following link:
Create and manage relationships in Power BI Desktop - Power BI | Microsoft Learn
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Best Regards
Yongkang Hua
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