I am looking for a set of the most appropriate questions to ask when users are terminating their subscription for a product or service. What would be a good number of questions and which questions are the most important to ask?
Edit: At the moment we are already asking a set of questions about - how often did you use the service - in which way did you use it - how successful you were based on the expectations you had when you joined - we are also asking the NPS question and - an open end question about what users missed from our service
I have also found quite many templates of these surveys while googling but what I am looking for is some advice or best practices about this kind of survey and how the answers are used later in product development.
We are using the feedback to see which features we are missing in comparison with our competitors but we are still missing information about why are people failing completing their goal with the service. Would it be useful to ask them to rate usability for example? Or some other very important question we have missed.