Issues with connection to web service

I have issues when I try to connect with my web service.I add the web reference and then in a main activity I try to access o the following way:

    public DataTable  QueryArticles(string pStrCodigoArticulo)
    {
        DataTable query = new DataTable (); 
        try
        {
            WsLoc09.WSActividad ws = new CallRestService.WsLoc09.WSActividad ();
            consulta=ws.QueryArticles (pStrCodigoArticulo);
        }catch(Exception ex) {
            throw ex;
        }

        return query;
    }

It is a example of a query where WsLoc09 is the name of my web reference. My web service is from visual studio. On the other hand, my issue appears when I run my app and in class reference.cs my app falls and say that "Error: connect Failure:connection is unreachable"

The previously code is on Main Activity...

I want to connect to web service and realize querys, deletes, inserts, updates on db from web service and opposite case.