Deleting your Memo account or uninstalling the app is not proof that subscription renewal was canceled. Billing needs a cancellation confirmation from the subscription provider.
Open iPhone or iPad Settings → your name → Subscriptions → Memo to check its status and cancel renewal. Use the Apple Account shown on your receipt.
If you can still sign in, open Settings → Subscription. If the account has been deleted or you cannot sign in, contact Memo support with the former Memo account email, receipt or invoice reference, billing date, amount and currency.
Say that the account was deleted and you need help locating and canceling its subscription. Do not create another paid subscription to solve this.
Ask for a separate review of the charge and include any earlier cancellation confirmation. A refund is not automatic. Follow Refund Policy for the correct request route.