Why have I been charged for more than my original invoice?

If an invoice remains unpaid past the payment deadline, we will charge the registered card for the full amount of the invoice, plus an increased Buyers Premium to cover the additional admin work involved. We will email the buyer to inform them that we have charged their card and we will ask them to acknowledge this by email. along with their address, so that the goods can be dispatched. For security reasons, we cannot ship these items until we have received this email response.