Try the options team on 0800 800 030. The robot woman asks you why you are calling - just say contract & yes.
You will need to re-contract for a year though in order to get the upgrade to a traffic management free contract:/
Quote this if they muppet at you:
http://community.bt.com/t5/BT-Infinity/Introducing-Totally-Unlimited-Broadband-from-BT/td-p/764984
I tried support and they were a bunch of retards. The tech support guy was clearly reading a script and had no clue what he was talking about. He had no understanding about the P2P throttling at all and outright refused to accept it was BT doing it.
Luckily though since I did that port-forwarding stuff that I found on the BT (or SE, forgot which) forums I haven't had any problems with it. If it does start to happen again though I'll have to look into that.