Question: May Allah be good to you, your Eminence, these numerous questions have come about the Prepaid card called Sawaa. This person says: I am a person who is not able to buy a regular cell phone or my family is not able because I do not have the continuous amount of money to pay the money bill or the price of calling. So like that, I use this type of card because I buy it when I can and benefit from it when I want. My question is: What is the ruling on my condition?
Answer: “If there is a specific time you have to you use it in, then it is not allowed. This is because they restricted its use to a duration of time. If the duration of time ends and you did finish using it, then it is wasted, without a right. It is not allowed. It is obligatory that if you buy something, that you use it until it ends. As for it to be said: it is not allowed to use it except for some days or a duration of time, if the time ends, it expires and the money remaining is not returned to you. If they said: they will return the remaining money, then there is no harm. As for them consuming it and taking it, then this is devouring wealth in falsehood. This is because if he buys something, he always owns it, not for an agreed time. He uses it until it finishes. This is the origin of buying and selling”
[Fatawa no. 3992 found here: https://www.ajurry.com/vb/showthread.php?t=7860]
Faisal Ibn Abdul Qaadir Ibn Hassan