Unable to log in with old personal password

Hi Guys,

Hoping someone can point me in the right direction here and help my client avoid having to purchase another office package. My user originally signed up her office account with her work email which at the time was an in-house Zimbra POP server. We finally managed to convince the company after many years to upgrade and go the hosted/office 365 route. Unfortunately this means the address my client signed up with now has a different login and license applied to it as per the hosted exchange and we can no longer sign into her old account to change details and activate her office after a hard drive crash and were forced to reload everything from scratch.

Does my client have any hope of changing the login details to another address so she may activate her product again? She is in possession of the original box and license key if this helps?

Thanks in advance