//create Billing for account
$session = $this->createSession($customer->getCustomerId());
$BudgetService =
$this->adWordsServices->get($session, BudgetOrderService::class);
$newBudget = new BudgetOrder();
//USD billing account
$newBudget->setBillingAccountId('xxxx-xxxx-xxxx-xxxx');
$newBudget->setPrimaryBillingId('xxxx-xxxx-xxxx');
$BudgetOperation = new BudgetOrderOperation();
$BudgetOperation->setOperator(Operator::ADD);
$BudgetOperation->setOperand($newBudget);
$res = $BudgetService->mutate([$BudgetOperation]);