Hi Katy,
Thanks for reaching out and so sorry about the trouble here!
I think the confusion is that Event Aggregator is a service and not a plugin that you install. In fact, it’s already included in The Events Calendar and you can activate it by navigating to Events > Settings > Licenses from the WordPress dashboard and entering in the license.
Once the license key has been entered, you will unlock Event Aggregator’s features and you will be able to start importing events by heading to Events > Import.
I also want to assure you that you were not charged for Event Tickets. It is a free plugin that we make available in all accounts by default, and I do not see an additional charge for it in your invoice.
Does this help clarify things a bit? Please let me know!
Cheers!
Geoff