Skype for Slack - Move your slack discussions to a group skype call
Meet Slack - Generate instant Google Meets by using /meet from any Slack channel, group or DM. Metings open with the correct Google Account and you Slack status updates to 'On a call' automatically.
Calls on Slack - Make voice calls in Slack
Slack - A messaging app for teams who see through the Earth!
Pingly - Your communication hub — Email, text & voice in one app
HandsFree 2 - Call and SMS in Mac using your Android phone via Bluetooth