Skype for Slack - Move your slack discussions to a group skype call
Walkie - Walkie is an online communication providing software that allows you to remain in touch with the other persons.
Calls on Slack - Make voice calls in Slack
Cord - One tap voice chat
Pingly - Your communication hub — Email, text & voice in one app
Slack Voice Chat by Standuply - Easily record and send voice messages on Slack 🗣️