Charges for subscriptions you never started can be scams, mistakes, or sneaky auto-renewals. Paste the notice for an instant read.
Whether you ever signed up, whether the sender is a real company you use, and whether the payment details and amount match anything you authorized.
Don't pay or click to 'cancel' via the notice. Check your own accounts/statements, and dispute unrecognized charges with your bank or card issuer.
Don't pay an unverified bill. Check your real accounts and statements, and if it's an unauthorized charge, dispute it with your bank. Treat 'cancel here' links in the notice as suspect.