Sets the PAYG billing settings for this client.

def set_payg_billing(self, currency, can_purchase_credits, client_pays, markup_percentage,
                         markup_on_delivery=0, markup_per_recipient=0, markup_on_design_spam_test=0):
        """Sets the PAYG billing settings for this client."""
        body = {
            "Currency": currency,
            "CanPurchaseCredits": can_purchase_credits,
            "ClientPays": client_pays,
            "MarkupPercentage": markup_percentage,
            "MarkupOnDelivery": markup_on_delivery,
            "MarkupPerRecipient": markup_per_recipient,
            "MarkupOnDesignSpamTest": markup_on_design_spam_test}
        response = self._put(self.uri_for('setpaygbilling'), json.dumps(body))