Classic Salesforce. The exact same thing happened with our org and Heroku. Zero empathy, just pony up or we trash your company.
Slack just did the same to us for our company Slack. We have to have the HIPAA compliant Enterprise version, price going up 40% next year. Looks like we'll migrate, especially because compliance has a bunch of annoying caveats.
The whole thing was super sleazy. We told them that we were moving to MS Teams (arrrgghhh!) and they said "Bye!".