[Drupal8] Bootstrap + Ajax button = fill content, one call.

order.routing.yml

order.subscription:
  path: '/subscription-test'
  defaults:
    _controller: '\Drupal\order\Controller\PinPukController::test'
    _title: 'Testing button'
  requirements:
    _permission: 'access content'

custom_ajax_link.routing:
  path: '/custom_ajax_link'
  defaults:
    _title: 'Custom Ajax Link'
    _controller: '\Drupal\order\Controller\PinPukController::ajaxSample'
  requirements:
    _permission: 'access content'

PinPukController.php

<?php

namespace Drupal\order\Controller;

use Drupal\Core\Ajax\AjaxResponse;
use Drupal\Core\Ajax\InvokeCommand;
use Drupal\Core\Ajax\ReplaceCommand;
use Drupal\Core\Controller\ControllerBase;
use Drupal\Core\Url;
use Symfony\Component\DependencyInjection\ContainerInterface;

/**
 * Class DealerOrderController.
 *
 * @package dsp_dealer_order
 */
class PinPukController extends ControllerBase {
  
  public function test() {

    $button = [
      '#type' => 'link',
      '#title' => [
        'icon',
        [
          '#type' => 'html_tag',
          '#tag' => 'span',
          '#value' => $this->t('Simkaart'),
        ],
      ],
      '#url' => Url::fromRoute('custom_ajax_link.routing', [], ['fragment' => 'customer-simcard-details']),
      '#attributes' => [
        'class' => ['use-ajax', 'btn', 'btn-primary', 'btn-block', 'simcart-ajax'],
        'role' => 'button',
        'data-toggle' => 'collapse',
        'aria-controls' => 'customer-simcard-details',
      ],
    ];
    $content['row'] = [
      '#type' => 'html_tag',
      '#tag' => 'div',
      '#attributes' => [
        'class' => ['row'],
      ],
      [
        '#type' => 'html_tag',
        '#tag' => 'div',
        '#attributes' => [
          'class' => ['col-md-4'],
        ],
        0 => $button,
      ],
    ];

    $content['holder'] = [
      '#type' => 'html_tag',
      '#tag' => 'div',
      '#attributes' => [
        'class' => [
          'panel-bordered',
          'panel-indication-right',
          'fade',
          'collapse',
          'no-collapse',
        ],
        'id' => 'customer-simcard-details',
        'aria-expanded' => 'false',
      ],
      [
        '#type' => 'html_tag',
        '#tag' => 'div',
        '#attributes' => [
          'id' => 'customer-simcard-details-content',
        ],
        '#value' => 'bfdbbe',
      ]
    ];

    return $content;
  }

  public function ajaxSample() {
    $response = new AjaxResponse();
    $response->addCommand(new ReplaceCommand('#customer-simcard-details-content', 'some markup'))
      // Toggle collapsed area.
      ->addCommand(new InvokeCommand('#customer-simcard-details', 'collapse', ['toggle']))
      // Remove event to prevent trigger ajax.
      ->addCommand(new InvokeCommand('.simcart-ajax', 'off', ['click']));
    return $response;
  }

}