Wowow! In this position my first step would be to determine if there's any legal basis for disputing the charge (an informal conversation with a lawyer or even just someone who's been through a similar experience is a fine start). Even when a billing change is disclosed in advance and the customer actually uses the bandwidth, massive spikes in metered pricing are a tricky area and have attracted the attention of regu…
Telecoms is a very heavily regulated industry.
> Also, immediately dispute the charge with your credit card company
No, don't do that. Most credit card companies require you to try and resolve the issue with the merchant before filing a chargeback. Sometimes they give you a time period, e.g. at least 30 days.