How to report & get refund for fraudulent charges?

An app has been charging me for months that I never signed up for. I only downloaded the app. I can even see that it's prompting me to sign up for a plan that I never did. I notified Apple by chat of the fraud charges and requested a refund. The senior advisor said there is nothing that can be done and ended the chat.

How do I report the fraudulent app, its unauthorized charges and obtain a refund? It's a lot of money - $487 Canadian.

How do I escalate this within Apple? Who is the right level and person/division to deal with?