Dependency inject a class with values from a config object?
Not sure which part exactly is unclear. There are lots of examples in core.services.yaml that inject the config.factory service to read a configuration object, for example this:

diff.formatter:
  class: Drupal\Core\Diff\DiffFormatter
  arguments: ['@config.factory']


The constructor for that then looks like this:

/**
 * Creates a DiffFormatter to render diffs in a table.
 *
 * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
 *   The config factory.
 */
public function __construct(ConfigFactoryInterface $config_factory) {
  $config = $config_factory-&gt;get('system.diff');
  $this-&gt;leading_context_lines = $config-&gt;get('context.lines_leading');
  $this-&gt;trailing_context_lines = $config-&gt;get('context.lines_trailing');
}


Once you have the config object, you get the configuration you want and pass it along to the SoapClient constructor.