remove phones from partnership

Good morning,

I received the following email from Microsoft:

You have 10 phone partnerships out of the maximum allowed 10 partnerships. After you reach the maximum, you can't create additional partnerships until you delete existing ones from your account. To do so, sign in to Outlook Web App, click Options > Phone > Mobile Phones, and delete any unused partnerships.

I would like to remove phones that we are no longer using from our account (partnership?)  Please let me know how to do that.

Thanks,

Dan