A second charge on the same day is usually a temporary authorization hold, not a real charge — it disappears on its own within a few business days. You can confirm by checking whether both lines show as "posted" or one shows as "pending" in your bank statement.
If two identical charges both post and remain, that's a genuine duplicate. Open Billing → Payment history; if you see two completed payments for the same period, request a refund on the extra one and it will be reversed to your original payment method.