Well there used to be SwapNote, but they've already removed that. I hope that Nintendo implements a new way to communicate with our friends, but I don't know if they have any plans to do so. Probably not.
I really liked SwapNote. The 3DS was the only way I could talk to some of my older friends who don't log on to social media sites anymore. Since they're gaming, they could just see the messages via SwapNote. I lost contact with many people after they removed it, but they did so for good reason, so I guess I can't complain.
swap notes was a useful messaging system but we need like a messaging application
for the 3DS that would be really useful i reason i made this thread is because me and a friend of mine play a lot of 3DS games but we have no way to talk to each other when we don't wanna play and just talk and no she does not have phone or any social media so it would be really useful