For help with the app, your subscription or your account, email support@biomarkersiq.com.
It helps to include the version of the app you are using, which is shown at the bottom of the Profile screen, and what you were doing when the problem happened.
Your subscription is billed by Apple. It can be cancelled or refunded at any time from your Apple Account settings, which is the only place a cancellation can take effect.
You can delete your account, and everything the server holds for it, from inside the app: Profile, then Delete account.