Shorten Subscription Still Attempting Charges After Cancellation

I previously had a subscription with the Shorten app, and I canceled it on my own request a long time ago. Despite this, for the past three days I have been receiving repeated messages stating that payment attempts failed due to insufficient balance in my account.

As far as I know, I do not have any active subscription or approved payment authorization. However, your system continues to attempt to charge my account and sends constant notifications, which is very disturbing.

I request that all memberships associated with my Shorten account, including any background subscriptions or payment attempts, be fully canceled. I also demand that no charges or debts be applied to me and that these messages stop immediately.