Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Best Buy needs some serious training here because they kept doing this to their customers. This is not the first time I am reading thread like yours where Best Buy refers to a billing/refund issue. You will need to get back to them and escalate it with the following article.
Microsoft explains it here: https://support.microsoft.com/en-us/account-billing/manage-your-microsoft-365-subscription-purchased-through-a-third-party-44749f45-4c0b-5d41-a73f-7634b8d2a763