Juan,
By default, Cesium connects to ion for both Bing Maps imagery and geocoding. The url you posted indicates Bing imagery (ion asset 2) is active. If you do not wish to use either of these and want to disable everything ion related, you need to pass options to the viewer widget:
var viewer = new Cesium.Viewer(‘cesiumContainer’, {
geocoder: false,
imageryProvider: false,
baseLayerPicker: false
});
Instead of false you can pass your own geocoder, imageryProvider or a custom selection of base layers for the picker; it depends on whether you are using these things in your application.
Hope that helps,
Matt