MSC Cruises review: No credit ever given for overcharge on wifi

As I understand it, they would return my overcharge if I agreed to download an app that I am unfamiliar with and have no history with. When I started the process, it appeared that I would be giving them monies instead of receiving a refund. I mentioned that to the customer service person and was told to trust him, and that I would not be paying but receiving a refund. Nowhere in the app did it show that, only that I was going to pay out over $500. When I did a search for reviews on this app, there were warnings that this app has had a history of scams.
I asked for a credit to my credit card or refund check and was denied. That is itself sends up a red flag.