Off the top of my head, Tracfone still operates like this in the US. As of 2018, they were selling service in "minutes", where one minute is also equivalent to 3 SMS or 1KB of data. The most common denomination is a 60 minute card for $20 (with a 90 day expiration), but in practice, many subscribers have a doubled minutes benefit for everything they add. They also have "just texts" and "just data" cards which offer better rates for those categories of service.
Tracfone targets themselves very narrowly at the "elderly and only want to pay for what I'll use/just want an emergency phone" demographic. If the subscriber is going to use the phone approximately at all, those are garbage rates, but if you only want to keep the lights on, $20/3 per month is about as cheap as it gets.
Tracfone targets themselves very narrowly at the "elderly and only want to pay for what I'll use/just want an emergency phone" demographic. If the subscriber is going to use the phone approximately at all, those are garbage rates, but if you only want to keep the lights on, $20/3 per month is about as cheap as it gets.