The only contact information I can find is this email for privacy requests, which should be good enough, they have to process legal requests they receive privacy@github.com
For Microsoft there is this Page https://www.microsoft.com/en-us/legal/policies AskCELA@microsoft.com
It's not clear from your messages whether you are a subscriber or your organization is a subscriber or both or neither. This affects how to access support and escalate and what claims you may have (your company should have a contract with access to enterprise support if they are customers).
It's not reasonable for GitHub to ban you with no justification and no recourse and make you lose your job.
Get a lawyer yourself. Or get your company to escalate through their support channel or legal.
Warning: We only have one side of the story. If you were posting abusive messages to Github in your name and/or in the company name, on company time. The company may review the messages and may find them abusive too and may fire you.