What is the ruling on buying prepaid cards for phone calls and selling them in installments for a commission, and is this action permissible or does it involve usury (riba)?

Purchasing prepaid calling cards is buying a known, permissible benefit. It is permissible to sell this benefit immediately or at a later time, for less or more than its purchase price, because it is not currency, so usury does not apply to it; rather, it is a benefit. For it to be sold in installments, an agreement on its installment price is required.