you Merkins are so removed from reality...
I'm speaking from having just spent the past month in Central America, riding the hot and cramped local buses and seeing people using almost exclusively Android smartphones (still some dumbphones). Is that what you call "so far removed from reality"? Regarding Africa, like I said, there will always be hold outs for whatever reason (battery life, simplicity, durability), but what you describe isn't really relevant to the topic, which is WhatsApp no longer being supported on older devices. Those people using missed calls for replies aren't even using the data connection on their phone, so they're not exactly going to be affected by WhatsApp not being supported on them, are they?
The sole reason why they like automatic payment so much is the cost of handling cash.
You fail to point out that handling credit cards costs money too: generally 2% of every retail transaction. If I were a small business owner, I'd want to have the choice whether or not I have to give 2% of all sales to some bank.
I don't know about you, but I find it rather disturbing that private banks are making ~2% of every single retail credit card transaction that occurs. That's skimming a shitload of money off of the world's economy for what is ultimately a convenience.