http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10618179
A few of my clients got caught out and cut down to dial up speed (which makes using a terminal server over the link a nightmare) and they are now issuing credits.
The article states the bung up was due to misconfiguration in preparations for tivo - which i think is zero rated against telecom data usage counters.