In MOST cases; whatever the original domain name was is going to be sintexinternational.onmicrosoft.com
The trial accounts do not expire for logging in and managing the Portal. access to any tool will be denied except domain management and user management.
Go to Portal.microsoftonline.com and enter sintexinternational.onmicrosoft.com then try whatever password you may have used previously.
Microsoft Online Services Technical Support can quickly search your technical contact email address you used to establish the account originally, as well as search the Domain name directly.
Another option is for Support to send a specific email to FrontBridge and request the domain be removed from the Admin Center.
Please respond to these posts so we know if you were resolved! Thanks!