Flo App Billing

The Flo App has been billing me for the past 3 months though I reportedly cancelled my subscription. I only have one account with the app and it’s not on a premium subscription. I also tried going on the app store but it said I canceled the subscription months ago. I don’t know what to do. They’re not responding and they’ve been charging me twice every month. Is it possible for me to get a refund on all these unauthorized payments?