If they are saying they cannot do anything then you are speaking to the wrong people,
I spoke to someone live on the web here (click on the link),
I told them that I have got the "Legend" achievement and I have been waiting 48 hours for the armour to appear with no luck. They then checked my account saw that I had the achievement and they said they had sorted it and sure enough when I got home it was there.
Try speaking to someone live and just tell them the above and they should be able to help, they did with me not sure why they couldnt do it with anyone else?
Hope this works for you,
Make sure you are logged into your xbox.com account when you start the chat