WorldPay is informed when to take a payment by the online store you set the agreement up with. If you want to change this date, please contact the online store directly. You should find the store contact details on the store's website, the store purchase receipt, and on the WorldPay transaction confirmation. Alternatively, email them direct using the Reply button on the receipt or the confirmation email.
When contacting the store, please include your purchase Recurring Payments (FuturePay) Agreement ID (displayed on the WorldPay transaction confirmation email).