That suck and I'm sorry to hear that. We're releasing public beta for built-in calling functionality on June 15 for both cloud and self-hosted offerings, you could give it a try to see if it meets your needs.

I'd also still like to help you setup tools that your team already use if it's still relevant. Please talk to us in the ~Ask R&D channel on our community instance: https://community.mattermost.com/core/channels/ask-r-and-d