Normally this wouldn't be that much of a problem, but with the ridiculously small number of API calls we can make, this is a big issue.

We want to get a list of invoices that a customer has not paid.  I tried doing things like status = "sent,overdue" but the API returned an error about invalid status.

This means that I need 5 API calls just to find out if a customer has unpaid invoices (sent, overdue, unpaid, partially_paid and viewed).

Is there an undocumented feature to 'return unpaid invoices', or is this what is expected?