The damage to your brand is immense.
It may be prudent to consider a wider, more serious, more comprehensive public response.
Mainly I'm turned off by the possibility that deleting all historical chat data for an organization in arrears is even an option. It costs nothing for Slack to store that data. That even this is a control knob in their organization is a huge red flag. A more reasonable approach would be "chats are read-only until your dues are cleared", maybe later escalating to "your users may not log in". Threatening to destroy IP to collect dues is crazy.
This should be treated like a massive data breach. No transparency = no trust.