So I phoned them up and got to a really crappy call centre where I couldn't actually make out what the person was saying due to background noise there, I mentioned this twice and the call centre advisor of course was unconcerned.
But basically I asked him (might have been a her due to noise I couldn't tell), oh wise Wanadoo minion, why oh why should I continue using your rather rubbish 512kb line for which i'm paying over the odds of £19.99 a month (as I applied really early on, if I applied now it would be £17.99/month) for this to get such horrible letters when you have my e-mail address and could have sent me a message as I was going over my useage limit rather then sending me a letter now it's too late and when British Telecom for the same price would give me a 1Mb line and better usage limits.
The call centre peon of course merely mumbled something about not being able to offer me anything but the packages.
So I hung up (saying, well thanks anyway) to them and have written an e-mail to Wanadoo asking for them to explain themselves or hey, it's off to BT I go.