In this post, I described how I found out that somebody had been using my AWS account for his own benefit. I received a first reply to my case
This is **** in the Escalations team at AWS Customer Service. I’m terribly sorry for any concern the unauthorized usage of your account may have caused, but it looks like you were able to terminate those compromised resources and re-secure your account again with help from my associate Nathan. That’s great! I will be handling your case from this point forward, and I’ll be sure to keep you updated along the way as our request to waive the unauthorized charges on your account progresses through the various levels of approval.
It doesn’t say a lot but at least someone is taking this seriously and will guide me through the entire process. Let’s hope all of this will get a happy end. Still not sure at this point in time to be honest.