Вам необходимо использовать http lib ниже.
Create Http Context host=www.app.com:8080 scheme=https
Set Request Header Content-Type application/json
Set Request Header Accept application/json
HttpLibrary.HTTP.GET /rest/api/customer/phone /personnalData
${Body}= HttpLibrary.HTTP.Get Response Body
JSON.Save Json ${Body} C:/RESTResponseBody.json