Reading/Saving JSON file on iOS issues

Hi

Following this tutorial, I need to read and write to JSON files on mobile...
https://learn.unity.com/tutorial/live-session-quiz-game-2

Tutorial says to put files in StreamingAssets folder.

This works fine for me in the editor (with the file in StreamingAssets)...

Code (csharp):

1.  
2. string filePath = Path.Combine(Application.streamingAssetsPath, "myfile.json");
3. if (File.Exists(filePath)){
4.             string dataAsJson = File.ReadAllText(filePath);
5.              myList = JsonUtility.FromJson<WrapperData>(dataAsJson);
6. }
7.  

But on device I'm getting a file issue:

nauthorizedAccessException: Access to the path "/var/containers/Bundle/Application/[appid]/myapp.app/Data/Raw/myfile.json" is denied.

at System.IO.FileStream..ctor (System.String path, System.IO.FileMode mode, System.IO.FileAccess access, System.IO.FileShare share, System.Int32 bufferSize, System.Boolean anonymous, System.IO.FileOptions

What am I doing wrong here?

Should I be using Resources instead of StreamingAssets?

Thanks