How to Contact Microsoft Privately for Windows Autopilot Deregistration?

We are a Canadian computer refurbishment company. We have legally purchased used computers that are still registered to previous organizations through Windows Autopilot.

We cannot contact the previous organizations and do not have Intune administrator access.

Is there an official Microsoft support email address or private support channel where we can request Autopilot deregistration and submit proof of ownership?

We are looking for a direct, non-public way to contact Microsoft's Autopilot support team without requiring an Intune subscription.