docs: 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))