Europe have free sms, so I do have friends with telegram, signal, skype, whatsapp, dumb phones, facebook chat, wire, etc., and at the the center of this crazy venn diagram, we can all discuss with sms for free. Most discussions are not group chats.

In Asia they have big whatsapp competitors like weechat. But I've seen kik used as well.

In Africa, it's also a lot of text message since they get the best coverage.

Whatsapp is definitly popular, but far from a universal.