In 9.1.3 we introduced a generic support for running any M3 API without having to create WS Stubs. If you are on a previous version you can still call a web service but it requires much more work including the use of Smart Office SDK. All calls to M3 APIs have to be done on a background thread!
There is simply no excuse for doing this the incorrect way. If you call the web service on the UI thread the entire UI will freeze for the time period that the call takes. In normal cases this will not be noticable but that does not matter. No calls to other servers on the UI thread.