how to get unbanned

You can always check through the Halo support, but unfortunately nobody here can assist you with getting unbanned on Halo MCC. I've never heard of anyone being banned because their game froze up though.....

Bungies system was pretty strict back in the day and 343i have a pretty solid stance on it too.

As others have suggested to wait it out and use the link provided above to contact them.

Its unfortunate that the system picked up on this in error as it was no fault of your own, however they have the system set that way to pick up on people using network manipulation and other forms of cheating. Did it give you any information on the duration
of the ban?

Sorry you've experienced this.

Halo was always been know to be aggressive with network manipulation. That's one of things I have always liked about the series is their stance on anti cheating. Unfortunately it looks like your issue mimics network manipulation. I don't believe Halo has
an appeal process. You might just have to wait it out.

If you've been banned, you would need to go to http://enforcement.xbox.com for information about your ban and to see about submitting a case review.

You should never post your personal information on a public forum.

If the console itself is banned there's nothing that can be done. A console ban cannot be reversed.