Server migration

About a week ago, I noticed that my emails in my folders were not populating.  They read: No Name and No Subject. This happened on both my MAC and when trying to access my emails in my folders thru webmail.  I called and reported the problem.  Said that they were changing servers and that some email accounts were effected by the change and mine would be escalated up  and it could take up to 72 hours to fix.

Two days later, I noticed that those same emails were no longer in my folders.  They were simply gone. I called, was told that they were still working on the problem and would contact me when resolved.

Next day received call from the tech. said that my emails problem has been resolved, but "some" emails were corrupted and unrecoverable. When I opened my folders, ALL of my emails had been deleted. When I called, they told me "sorry". can't get them back. Told me that I should have used a back up service. All good and fine, if I was the one doing the migrating of my own emails.  No one from cox told me  that they were changing servers and/or that we may experience some delay, and/or problems. Was told nothing that they can do. 

 Has this happened to anyone else? What to do?