Is selling mobile phone scratch cards electronically, with the price determined by immediate and deferred payment options that suit the customer, Islamically permissible?

There is no harm in selling phone credit for more than its value, because it is a utility that can be sold and profited from. It does not have the ruling of currency. The evidence for this is the fatwa (definition) of the Permanent Committee permitting the buying and selling of this type of phone card, because its reality is the sale of a permissible utility.