Allowing others to use my account

So on 18th Aug I notices collections and deliveries being done on my cash account. I informed them that they where allowing someone else to use my account without my permission. I was not worried about it too much, its a simple credit they need to do. Its now getting close to a month and they still do not want to do the credit from my account before the other person pays. When asked 3 times what the reason is for me not getting my credits, they still do not give me an reason. They actually can not answer the question. Needless to say, they can deliver and collect. But they sure as hell can not do a simple credit