Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hello
You would have to cancel the Family subscription and subscribe the personal plan separately.
In general, the family plan still is in effect until it expires.
But, if you signed up for the family plan during the last 30 days, ask for a refund, go to https://support.microsoft.com/contactus, Type "Billing" and press Enter. On the next screen, click "Contact support" at the bottom of the page, then choose "Microsoft 365" > "Manage my subscription". You’ll then see the option to chat with a Microsoft support agent who has access to your account to help review the issue.
You can reference this detail step by step instruction with screenshots I posted in this thread: https://learn.microsoft.com/en-us/answers/c/2714817
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Otherwise if you live in one of these countries, you can ask for prorated refund. https://support.microsoft.com/en-us/account-billing/countries-with-prorated-refunds-for-microsoft-subscriptions-38c81df4-10c1-f3eb-8d2f-b04f980c435f