Possible hacked email account with Microsoft Univeristy 365 Ooffice Word product key

I believe that my email account has been hacked as I am unable to log in with the correct details. I was able to sign into the account over the weekend when I bought Microsoft University 365 Office word and then the next day I could not log into the account. I have tried to reset the password but the account was only created last week and so has not sent any emails. Also, the email address to which the reset link would be sent to is not an email of mine. I need this to be sorted out because I have paid for Microsoft Office 365 Word and the product key was sent to this account. How do I go about resolving the issue?