What is a "plan" ?

It is a "nice to know" information for the customer about their subscription. It is visible for the customer, when they click on "Aftale" under "Abonnementsbetalinger" menu. The purpose is to inform the customer, what they are paying for. 

What is it used for? It depends on the customer's business model. For 3 Mobile, the plan could be defined as "Mobil and Bredbånd", since that is what the customer is paying for.  

Is it a mandatory field? Yes - especially from a customer perspective, as it is nice for the customer to be able to go into the app, to see which product or plan, they are paying for. It is a required field in terms of MobilePay Subscriptions. 

Are there default values? for example: Basic, Medium, Super? There are no default values. The merchant decides the values, as they know best, what their customer is paying for. For example: a newspaper can have the value "Digital" if it is a digital subscription and "Paper" if it is a paper-based subscription.