title: CTTelephonyNetworkInfo returning nil on iOS 12
body: <p>I have the following code: </p>
  
  <pre><code>let networkStatus = CTTelephonyNetworkInfo()
  
  func getCellularInfo() {
      if #available(iOS 12.0, *) {
          var info = networkStatus.serviceSubscriberCellularProviders
          if let aKey = networkStatus.value(forKey: "serviceSubscriberCellularProvider") {
              print("aKey: \(aKey)")
          }
      }
  }
  </code></pre>
  
  <p>This code retuns: </p>
  
  <blockquote>
    <p>aKey: {
        0000000100000001 = "CTCarrier (0x28282e610) {\n\tCarrier name: [Vodacom]\n\tMobile Country Code: [655]\n\tMobile Network Code:[01]\n\tISO Country Code:[za]\n\tAllows VOIP? [YES]\n}\n";
    }</p>
  </blockquote>
  
  <p>I am not familiar with this method, how do I obtain the values associated with the keys, for example <code>\n\tMobile Country Code: [655]/n/</code></p>