Cell networks are only semi-reliable here, a significant portion of people don't use smart phones (or really care about their phones), and that also needs to be linked to some electronic "value store".
Sure, it's possible to overcome all of these things in theory - but at what benefit to the population? Cashless payments are not a goal in and of themselves.
You don't need a smartphone to enable cellphone financial transactions, check out Kenya's Safaricom Mpesa https://en.wikipedia.org/wiki/M-Pesa which is SIM card based, doesn't use any data, has the option of using USSD or Mobile App. It's already available in Egypt.
What do University of South Sudan denars have to do with Kenya?