Originally Posted by
mecabq
I have a little bit of credit for an unused portion of an entirely domestic trip. ...
So this is a partially flown trip credit
Originally Posted by
mecabq
, the agent told me that I can't use this credit for an international itinerary....
Likely true, the credit can only be used for a flight consistent with the original fare rules. This is only when you are using the credit for a partially flown trip. Those credits can be very hard to use.