Since your question is in English, I'd like to reply in English for clarity.
Dear @Stanislav M,
Good day! Welcome to Microsoft Q&A forum!
Based on your description, I understand that you’re unable to cancel your Power BI Pro subscription because the only global administrator account is inaccessible. The former admin has left the company, and the associated MFA device is unavailable, so billing continues despite no account access. You’ve created a new tenant under a new domain, while the old tenant remains active and billing. You’re requesting help to remove the payment method and cancel the subscription on the old tenant and can provide invoices and domain ownership proof to verify your request.
Regarding this matter, since you have created a new tenant, you should be able to access the support portal and submit your ticket referencing your locked account without further issues.
In the ticket's description, you could refer to this message "Hello,
I am unable to manage or cancel a Power BI Pro subscription because the only global administrator account for the tenant is no longer accessible. The former employee who owned the admin account has left the company, and we do not have access to the associated multi-factor authentication, which prevents us from accessing the Microsoft 365 Admin Center or stopping billing.
To resolve this, I have created a new tenant and would like to be connected with the Data Protection Team to verify my identity and assist with regaining access. I am available to provide any required documentation or verification to support the recovery process."
Ticket Support: Log in the Microsoft 365 Admin Center using your newly created admin account for the new tenant > Support > Help & Support. You can raise support ticket at: https://admin.microsoft.com/#/support/requests
Please remember to cancel the trial subscription once your issue is resolved to avoid any unintended charges.
I hope this information is helpful.
Kindly let me know when there are updates or if you need further assistance.
Thank you for your time and patience.
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