Slicers Across Datasets

I have imported multiple tables (all Excel) into Power BI

I have connected them through a text variable "Customer Name"

In one of the tables, I have 3 columns, "Customer Name, "Service", "Y or N" indicating if we provide the service or not. There 4 rows per customer

When I add a slicer in for "Customer Name from any of the tables", all of my visuals change accordingly

When I add a slicer for another variable in a table where I only have one row per customer, my visuals change accordingly

However, when I add the slicers "Service" and then drilled down into "Y or N", my visuals don't seem to change. E.g. say there is a service called "Postal" and there is a "Y" corresponding to 3 customers, when I select "Y" under "Postal" in the slicer, it does not filter for the 3 customers

How can I create this slicer? I have freedom to edit the source data in any way - it's all dummy data on Excel