If you would like to remove your connection to a medical organization without deleting your account, you can do so from the Connections screen, which is accessed by clicking "My Account" in the top right corner and selecting "My Connections" from the drop-down list.
Click the "X" next to the organization's information (circled in red in the image below).
You will be given a warning box that if you remove the connection, you will no longer receive updates to your health record (see image below). Click "Yes" if you are sure you would like to disconnect.
Note: Removing the medical organization from your account will prevent new information from flowing to your portal from that organization. If there is older medical information, prior to the removal, that will stay in your portal and does not get erased/removed.