Amazon have transferred £3869 to a third persons account!

We need help on what to do next!!

In September, our UK seller account was hacked and it was 2 weeks until we were aware of the hacking. An unknown hacker managed to get into our account and change the bank account details on the account. We were not notified of this by Amazon at all (even though if we change anything on the account, we get sent a notification). Fortunately the hacker also tried to apply for an Amazon lending loan in our name and the person dealing with the application noticed that the bank account had been changed just prior to the application. It was him that notified us.

Unfortunately during the time that the bank account was changed, Amazon transferred £3869 into it from our seller account! Despite being assured that this case is being investigated, we have received absolutely no communication from anyone associated with any investigation. We have not received the money back and are now at a loss of what to do next! Whenever I reopen the case, if just gets closed again and marked as answered!

Any ideas on what to do next?

Similar thing happened to us. Our account was hacked on 28th of October and hackers refunded 33 orders to the customers which was worth £3886.11 and deleted all the orders from amazons sellers history. Most of these orders were completed.
We have written so many emails to amazon but they have not been able to do nothing until not. Every time we contact them regarding this, they give us a new reference number and tell us that its been forwarded to our fraud team and they will contact you but no one did. Since they we are not able to sell on amazon because our account is showing in minus. Its at a stage where I am very frustrated because amazon is going nothing to help us out.
We have got a complete record of emails from amazon assuring us that it will be resolved but nothing has until not.
Can anyone please suggest us what to do now?