If you need to get reset due to a hack there is nothing you can do. Nothing Activision can do. They COULD ban you for boosting or hacking for example but they cant reset your score.
Over the past month there has been a ton of people saying "I accidentally got put into a modded lobby" while their Gamertag was posted all over on modded sites.
One guy for example got caught then denied it then claimed his brother was at fault.
You MIGHT be able to post your Gamertag and perhaps tech support might help, but no guarantees.
But I can safely assume the answer is the same answer your other post got about 2 weeks ago in the same forum which is dont accept random game invites