This is a Virtuoso affiliated agency on the east coast of the USA. Very high service. It's not an OTA with an off-shore call center. They have a dedicated after hours service located in the same area as their main office.
The flight was chosen because it was a great connection and sold as DL on both flights.
DL7480 AGP 10:35am AMS 1:40pm Operated by Transavia
DL9223 AMS 4:55PM BOS 6:30pm Operated by KLM

Delta ended up reticketing them the same day on this;
True KL AGP-AMS
overnight
True DL AMS-BOS
As I mentioned, they did charge $140 per passenger additional collection because they said it must be considered a voluntary change unless the agent in AGP could put in the record what was the problem or at least the amount due.
HV's ground operator in AGP, Aviapartners, said they could not make those kind of updates to the record.