diff --git a/app/Main.hs b/app/Main.hs
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -10,6 +10,7 @@
 import Speechmatics.Client 
 import Network.Mime(MimeType)
 import Data.Text(pack, Text)
+import           Data.Aeson                  (decode)
 
 data MainOptions = MainOptions
     { 
@@ -41,6 +42,12 @@
   let mime = (defaultMimeLookup "d.mp3")
   print mime
   print . sha256 $ bytes
-  result <- runStdoutLoggingT $ transcribeBytes (ByteConfig (Location JsonV2 "http://192.168.38.91:8082/v1/user/" userId Nothing) "en-AU") (LoadedFile bytes file mime)
-  putStrLn . show $ result
+  case decode "{ \"type\": \"transcription\", \"transcription_config\": { \"language\": \"en-AU\", \"diarization\": \"channel\", \"channel_diarization_labels\": [\"Agent\", \"Caller\"] } }" of
+    Just json -> do
+      result <- runStdoutLoggingT $ transcribeBytes (ByteConfig (Location JsonV2 "http://192.168.38.91:8082/v1/user/" userId Nothing) 
+          -- "{ \"type\": \"transcription\", \"transcription_config\": { \"language\": \"en-AU\", \"diarization\": \"channel\", \"channel_diarization_labels\": [\"Agent\", \"Caller\"] } }") 
+          json) 
+          (LoadedFile bytes file mime)
+      putStrLn . show $ result
+    Nothing -> return ()
 
diff --git a/speechmatics.cabal b/speechmatics.cabal
--- a/speechmatics.cabal
+++ b/speechmatics.cabal
@@ -2,10 +2,10 @@
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: db9c3ccd92a7f21fe5f04addcde9142dba3b2245ec662671ddb9d0acb2494fee
+-- hash: cc509a2a8595bbf451ac07ba7f538d6fce13a779255b88f9e04880c1420bb01b
 
 name:           speechmatics
-version:        0.5.0.0
+version:        0.6.0.0
 synopsis:       Speechmatics api client
 description:    Upload audio files to speechmatics to get a transcription
 category:       API
@@ -55,6 +55,7 @@
   ghc-options: -threaded -rtsopts -with-rtsopts=-N
   build-depends:
       SHA
+    , aeson
     , base >=4.7 && <5
     , bytestring
     , mime-types
diff --git a/src/Speechmatics/Client.hs b/src/Speechmatics/Client.hs
--- a/src/Speechmatics/Client.hs
+++ b/src/Speechmatics/Client.hs
@@ -6,7 +6,6 @@
   transcribe,
   AuthToken,
   UserID,
-  ModelName,
   LoadedFile(..),
   Error(..),
   Format(..),
@@ -23,7 +22,7 @@
 import           OpenSSL.Session             (context)
 
 import           Data.Aeson                  (FromJSON (parseJSON), Value,
-                                              eitherDecode)
+                                              eitherDecode, encode)
 import           Network.HTTP.Client         (defaultManagerSettings,
                                               managerResponseTimeout,
                                               responseTimeoutMicro)
@@ -85,7 +84,7 @@
 -- | Configuration data for transcribeBytes function
 data ByteConfig = ByteConfig {
   location :: Location,
-  model    :: ModelName
+  config :: Value
 }
 
 makeOpts :: Options
@@ -103,14 +102,15 @@
 -- | Transcribe a file that is already loaded in memory
 --   Does not catch exeptions
 transcribeBytes :: ByteConfig -> LoadedFile -> LoggingT IO(Either Error Value)
-transcribeBytes (ByteConfig location model) (LoadedFile content filename mimetype) =
+transcribeBytes (ByteConfig location config) (LoadedFile content filename mimetype) = do
+  debug $ pack $ show parts
   transcribe location defaults parts
   where
     parts = [
         partLBS inputName content
           & partContentType ?~ mimetype
           & partFileName ?~ filename,
-        partString modelName model
+        partLBS "config" $ encode config
       ]
 
 withAuthorization :: Options -> Options