First some background. Your Microsoft Account is not your Business Office 365 account, they are two completely different accounts. One owned by you as an individual and the other manged by your company.
Until recently you could use your work email as the username for your Microsoft account, but as of September 2016 this is now not possible (it was a long time coming).
Sharing the same email address leads to confusion and multiple logins. To change this you need to change the username or alias you use for your personal account.
Microsoft outlines the steps to follow on their blog and they are summarised below:
Sign in to the Your Info page of your Microsoft account.
- If your work or school email address is the only one listed, enter your personal email address or get a new one from Microsoft, and select Add alias.
- If you already have a personal email address listed there, you can skip this step.
- Look under the Account aliases section.
- Select Manage your sign-in email or phone number.
- If your personal email address does not have (primary alias) listed next to it, select Make primary to set it as your primary alias.
- Select Remove next to your work email address to remove it from your account.
However there are a few gotchas
- It is not possible to merge accounts, so if you have already created a Microsoft account for the email address you want use, you will need to move your data from one account to another, then close the account. Closing an account takes 60 days.
- If you want to create a new email as your sign in email, you can create a free Outlook account and use this. It takes about 48 hours for your alias to change.
Note that if you create a new Outlook account then you have another email address to monitor, so you may want to auto forward your new Outlook account to your existing personal email so you receive important Microsoft account notifications etc.