Billing account disabled for suspicious activity, cannot create a support ticket

My Azure billing account and subscription were disabled with the message "We've identified suspicious activity in your subscription." The subscription is in state Warned, and write actions fail with the error ReadOnlyDisabledSubscription. Context: - All invoices are paid and there is no amount due. - There is no Azure service health incident. - The Reactivate page only says to contact Azure Support. - The Support + troubleshooting wizard ends at the automated "Account review" step, with no option to submit a ticket (I tried both "Billing" and "Subscription management"). - Phone support redirected me to a website, and the Microsoft chat sent me to Engage Center, which shows "No access" for my personal Microsoft account. How can I reach the Azure billing/security team to request a review and reactivation of the account? Please also tell me what information or documents are needed from my side.