How do I make a descriptive flexfield populate with the default on corporate card transactions?

Summary:

Descriptive flexfield not populating with default value on imported corporate card transactions

Content (required):

I enabled a descriptive flexfield to track business purpose on expense items. Values are selected from a list, with "General or N/A" as the default. This field is configured as required. When creating an expense item manually, the field is correctly populated with the default value. However, imported corporate card transactions come in with that field blank, so users have to go in and select the value. Of course, if they need to set the value to something other than "General or N/A" they'd have to modify the item anyway, but for those items where "General