Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
Hello, good day and thanks for your question. I understand that you have a query for your Microsoft 365 subscription.
You do not need multiple subscriptions not unless you are already over the limit for it and the existing ones you have can still be used for your new computer if you login at account.microsoft.com/services and install it on your new computer
As you have an existing subscription, you can cancel it and then you can go to https://account.microsoft.com/services/microsoft365/billing and try it from there or try to turn off the recurring billing at https://go.microsoft.com/fwlink/?linkid=2277073 and you can also follow the guided steps indicated from the link below which also includes refund eligibility check.