toolani - Cheap international calls
Skype for Slack - Move your slack discussions to a group skype call
KeepCalling - Best Rates for International Calls. No Contract, Expiry, or PIN. Use Any Phone, Smartphone or PC.
Aircall Now - Make voice calls inside Intercom Messenger 📞💬
Rebel Calling - Internet-free international calling for $1 a month
Slack - A messaging app for teams who see through the Earth!