Here are instructions on how to change the partner of record (POR) for your Office 365 account. These instructions are meant for end-user subscribers.
IMPORTANT: Before you begin, you must have the Partner ID of the Microsoft partner that you wish to switch to. There can only be one partner listed per subscription.
Login to the Office 365 admin portal with your Administrator credentials
On the left navigation, click on BILLING | Subscriptions
Then go to More Actions and click the down arrow
Click Edit partner of record
Now, type in the partner ID and click submit.