Is phone credit treated like cash when deducting its value from purchases?

The contract between the customer and telecommunication companies is a lease contract (ijarah (definition)), where the customer owns the usufruct (the balance) and is permitted to dispose of it through buying and selling, such as purchasing goods with part of their balance. This is permissible, as it is not a condition for a sale to be transacted with cash. If the company requests a fee in exchange for the service of transferring the usufruct, there is no objection to that.