They absolutely intend to refund it WHEN you ask. OP just did not use the right protocol to ask. I agree with others that this is a BIG issue and only a select few (mostly FTers) know what to do to get the erroneously charged tax back. Filing DOT complaints would hopefully help, but the issue is likely that so few affected passengers will EVER know they are owed money that there will not be enough DOT complaints to force change.