Microsoft 365 features that help users manage their subscriptions, account settings, and billing information.
You can check this primary thread having suggested solutions by experts: https://community.office365.com/en-us/f/156/t/401582
This is also happens due to failed move requests are not yet removed from the system check this article that might helps you:
https://support.microsoft.com/en-us/kb/3050691
Clearing out mailbox move requests:
http://thoughtsofanidlemind.com/2010/11/22/clearing-out-mailbox-move-requests/
You may also take help from this article having list of Office 365 Migration Issues and resolutions
Hope it helps you!
Off-the-topic, while need to migrate user mailboxes from exchange to office 365, you may try also this <link removed> solution which lets you to accomplish this migration task without any interruption.