Payment::updateAction

public function updateAction(BitrixSalePayment $payment, array $fields)
{
	$data = [];

	$fields['ID'] = $payment->getId();
	$fields['ORDER_ID'] = $payment->getOrderId();

	$data['ORDER']['ID'] = $fields['ORDER_ID'];
	$data['ORDER']['PAYMENTS'] = [$fields];

	$builder = $this->getBuilder(
		new SettingsContainer([
			'deletePaymentIfNotExists' => false
		])
	);
	$builder->buildEntityPayments($data);

	if($builder->getErrorsContainer()->getErrorCollection()->count()>0)
	{
		$this->addErrors($builder->getErrorsContainer()->getErrors());
		return null;
	}

	$order = $builder->getOrder();

	$r = $order->save();
	if(!$r->isSuccess())
	{
		$this->addErrors($r->getErrors());
		return null;
	}
	if($r->hasWarnings())
	{
		$this->addErrors($r->getWarnings());
		return null;
	}

	/** @var BitrixSalePayment $entity */
	$entity = $order->getPaymentCollection()->getItemById($payment->getId());
	return ['PAYMENT'=>$this->get($entity)];
}