SSAS Cube Only Displays Total Values

When browsing my cube it shows the correct invoice values by date when I select only a date type (the date table was generated by SSAS with hierarchies), but if I add the customer name it shows the combined value of the invoices for the date period, rather than the total per customer. I expect to see the total value for the customer that month, not the overall monthly total. My tables are joined with foreign keys and the DSV shows a star schema. A simplified version of the schema is below. factInvoice invoicePK customerFK -> customerPK dateFK -> datePK dimDate datePK dimCustomer customerPK The dimension usage tab shows both dimensions are linked to the invoice table. Please can somebody shed some light on why this is happening? I'm sure I'm missing something pretty basic here! Thanks.