Initialization error when calling a function in an imported helper file

After writing a lot of TypeScript form logic held in multiple files, I thought I would include all my common functions in a helper.ts file. Getting it wired up is proving a bit difficult. Be interested in hearing any advice.

I have set up simple project structure for an app. To start with I have 2 files

1. utilshelper.ts

      // show a simple dialog
      export function displayPromptText(titleText : string, promptText : string)
      {
        let alertStrings = { confirmButtonLabel: "Ok", text:promptText, title: 
        titleText  };
        var confirmOptions = { height: 400, width: 450 }; 
        Xrm.Navigation.openAlertDialog(alertStrings, confirmOptions).then(  
        function (success) {    
   
        console.log("Dialog closed using OK button.");
        }, function (error) {
         console.log(error.message)
      }  
   
    )   
   }
   

2. FormsMyForm.ts

     import * as helper from  "../utils/helper"
     // also tried this
    // import { displayPromptText } from "../utils/helper";
   
   
     // if you call the line below say in Form load you get the intialisation error 
     helper.displayPromptText("test","test");