Currently, Microsoft does not offer a standalone plan that allows users to pay solely for OneDrive storage without including other Microsoft 365 services. However, OneDrive storage is included as part of Microsoft 365 subscriptions, which also provide access to Office applications and other services. If you are already paying for additional storage (like the 1 TB you mentioned), you should retain that storage as long as your subscription remains active.
If you are looking for more flexibility or specific storage needs, you might want to explore the options available through Microsoft 365 Extra File Storage, which is designed to provide additional storage capacity beyond the standard limits included in Microsoft 365 plans, particularly for educational institutions.
For personal use, you may want to consider the various Microsoft 365 plans that include OneDrive storage as part of the package, as there isn't a separate option just for storage without the other services.