Basic Economy should only be available via UNITED directly and not though other outlets which would probably help the Expedia issue and not knowing that one bought Basic Economy without knowledge that they did so.

How you fix communication issues is beyond my scope of knowledge, there are business folks who know far more about than I do.

Essentially, it seems that was what my Father experienced was a poorly communicated instruction that should have been made abundantly clear, but for whatever reason was not and employees were able to interpret the instructions on their own.