Additional features, settings, or issues not covered by specific Microsoft Teams categories
Hi SamKuiper,
As a matter of fact, Teams premium is not a standalone production. It's a part of Office 365 subscription. And Office 365 subscription provides an initial domain xxx.onmicrosoft.com for the first registration. This is a domain provided by Microsoft. If you cancel the subscription, you cannot use this domain anymore.
As for Teams free, it uses Microsoft personal account for registration instead of Office 365 account. You can neither use an Office 365 account to sign in Teams free services, nor use Microsoft account to sign in Teams premium. Besides, after the subscription cancelled, your Office 365 account will be invalid after 90 days. So if you just want to use Teams free, please kindly sign up Teams free with your Microsoft account.
Regards,
Marvin