ChannelData {{
  "channel": {
    "id": "19:5e4ce488280b467198400257473cfd4e@thread.skype"
  },
  "team": {
    "id": "19:7a81d1b1c0b24ac192de1c3d5cfd5618@thread.skype"
  },
  "tenant": {
    "id": "8c6ae172-a3ea-4f50-994d-a0256822697f"
  },
  "source": {
    "name": "compose"
  }
}}

GraphServiceClient graphClient = new GraphServiceClient( authProvider );

var replies = await graphClient.Teams["303d2c1c-f1c5-40ce-b68e-544343d7f42b"].Channels["19:fec4b0f2825d4c8c82abc09027a64184@thread.skype"].Messages["1555375673184"].Replies
    .Request()
    .GetAsync();