Thanks everyone for your insights, it is very interesting to read how the ANC locations are so independent of the national chains, and not just AVIS.

I hate to to shock you any further but the refund posted! All it took was a friendly request by email and they immediately responded that the refund would be made. Apparently this was in the pipeline to be processed when I mailed a reminder but now it is all done.

It seems that they know they should not have charged this extra amount and simply count on people not following up. But that's the power of Flyertalk, it has given me the background, knowledge of the rules and how to follow-up. And it all worked out this time. Thanks guys!