Voice memos

These messages are sent almost exclusively through WhatsApp, which has around 11 million users in Argentina. Federico Novick, who is from Buenos Aires and is doing graduate research in Internet Studies in the US, said many people in Latin America use WhatsApp instead of SMS because it’s relatively cheap.

“The main reason people use WhatsApp in Argentina is because in many Latin countries, you have to pay for every text you send,” he said, “whereas with WhatsApp, you pay one price for data and you can send as many as you want.

From Vice.com

I've never once received a voice memo as far as I can remember. But I've also never received any messages through Line, WeChat or any of the multitude of other massive messaging/communication platforms out there - many of which have several hundred million active users. Interesting how different regions picking different preferences.