It sounds like they gave you a feature for free you didn't want, and now are trying to charge for it. Very much a dark pattern.

The person writing this doesn't have the feature. It would have had to be enabled by someone on a GitHub org they were a member of.

It's not even available on personal free plans like the person says they have. Either the e-mail was sent in error, or it's enabled by someone else in an organization they're a member of.