Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
It isn't possible to merge Microsoft accounts. I would suggest that you cancel one of the subscriptions. See https://support.microsoft.com/en-us/accounts-billing/subscriptions/cancel-a-microsoft-365-subscription .
Note that not all cancellations will result in a refund. For example, if one of the subscriptions is (say) a prepaid one-year subscription, you may not be able to cancel, so you should keep that one. Read about refunds in the article at https://support.microsoft.com/en-us/accounts-billing/subscriptions/how-to-get-a-refund-on-a-microsoft-subscription .