Microsoft Teams Free admins began receiving emails last month stating that their ‘trial’ was expiring. Users would delete data if they did not purchase a paid subscription. Microsoft is assuring that only organizations that have not been in use for a total of 120 days will be deleted. Active Teams Free organizations will not be deleted if they are actively used. Microsoft introduced a new method to clean up inactive Microsoft Teams organizations by warning admins that Microsoft would begin closing accounts and ultimately deleting data for being inactive over the past 90 days.
Source: https://www.bleepingcomputer.com/news/microsoft/no-active-microsoft-teams-free-organizations-will-not-be-deleted/