protected function update_session( $data ) {
		// Update both shipping and billing to the passed billing address first if set.
		$address_fields = array(
			'first_name',
			'last_name',
			'company',
			'email',
			'phone',
			'address_1',
			'address_2',
			'city',
			'postcode',
			'state',
			'country',
		);

		array_walk( $address_fields, array( $this, 'set_customer_address_fields' ), $data );
		WC()->customer->save();

		// Update customer shipping and payment method to posted method.
		$chosen_shipping_methods = WC()->session->get( 'chosen_shipping_methods' );

		if ( is_array( $data['shipping_method'] ) ) {
			foreach ( $data['shipping_method'] as $i => $value ) {
				$chosen_shipping_methods[ $i ] = $value;
			}
		}

		WC()->session->set( 'chosen_shipping_methods', $chosen_shipping_methods );
		WC()->session->set( 'chosen_payment_method', $data['payment_method'] );

		// Update cart totals now we have customer address.
		WC()->cart->calculate_totals();
	}