A variety of methods exist to block access to a user’s Office 365 (Azure AD) account from a complete block to a conditional access policy. In this article, we examine the various methods and debate the worth of each approach. Conditional access policies are the cleanest and most effective long-term solution, but you need Azure AD premium licenses. If you don’t have those licenses, maybe one of the other approaches will work for you.
https://practical365.com/how-to-block-user-access-to-office-365/
