I've actually have had similar experiences before where my rank would rollback. I did some research and found this helpful link: Activision Support
Just try out the things in there. For me, what I did was that, I wait a few moments, make sure that the match was over and after doing a few references from the link, the rollbacks only happens once in a blue moon and they're very minimal. 1-3 levels. 4 at the most. Hope this helps out:
I agree with Crinkzkull08, also if you are using a wireless connection and keep on disconnecting it can also cause this issue. Try to use a wired connection for the game, it worked on me and this issue never happened to me either.