Class method

CMS.DataEngine.InfoDataSet<CMS.Chat.ChatOnlineSupportInfo> CMS.Chat.ChatOnlineSupportInfoProvider.GetOnlineSupportEngineers(System.String, System.String, System.Int32, System.String)

was removed. Use object query method

GetChatOnlineSupportEngineers

instead. See http://devnet.kentico.com/articles/kentico-8-technology-dataquery-api for more information.