Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hello
The basic plan gives you 100GB for your hotmail storage, which is the 100GB shared with OneDrive,.
If you cancel it, your hotmail is down to 15GB with 5GB of OneDrive storage.
Go to https://account.live.com, sign in, and expand the section called "Microsoft storage", what's your current storage usage? If you use more than 15GB for mailbox and 5GB for OneDrive, then canceling it will affect your hotmail.com functionality. But if you use under those numbers, canceling it will not affect anything.