Android Question NetworkOnMainThreadException on 3G data, not on WiFI

hc.Initialize("hc")
Dim req As HttpRequest
req.InitializeHead(MapDownloadLink)
hc.Execute(req, 1)

Sub hc_ResponseSuccess (Response As HttpResponse, TaskId As Int)
   Log("Map file size: " & Response.ContentLength)
   CurrentMapSize = 342342342 'Response.ContentLength
   If AreNevoieDeHarta = False AND File.Exists(MapFolder, "Map.nfo") Then
          Dim sMapSize As String
        Dim OldMapSize As Long
     
        sMapSize = File.ReadString(MapFolder, "Map.nfo")
        If IsNumber(sMapSize) Then
            OldMapSize = sMapSize
        Else
            OldMapSize = 0 
        End If
        If OldMapSize <> CurrentMapSize Then
            Dim Answ, CodAnsw As Int
            CodAnsw = 0
            Answ = Msgbox2(Proceduri.MsgNewMapAvailable, Proceduri.Title1, Proceduri.ChooseYes, "", Proceduri.ChooseNo, Null)
            If Answ = DialogResponse.NEGATIVE Then
                CodAnsw = 1
                Return True
            Else
                CodAnsw = 2
            End If
            If CodAnsw = 2 Then
                'Utilizatorul doreste sa descarce noua versiune
                DescarcaHarta
            End If
        End If
   End If
   Response.Release
End Sub

Sub hc_ResponseError (Response As HttpResponse, Reason As String, StatusCode As Int, TaskId As Int)
  Log("Map info error: " & StatusCode)
  Response.Release
End Sub

CurrentMapSize = 342342342 'Response.ContentLength

Dim CurrentMapSize As Long

Dim hc As HttpClient