Vodafone over charging for phone bill what can i do.

I am a premium customer of vodafone since 8 years, monthly bill usually goes till Rs. 2000 a month. I was traveling to Moscow, Russia so i called at the customer service center and inquired about International Roaming Packages, they gave me all the details and i crossed confirmed that the package i m selecting is valid in the country or not,The person on call said yes and therefore he activated the package. Then at the end of the month the bill came. And to my shock it showed Rs. 25,400. I called at the customer service center and got the reply that you have to pay thr bill because the roaming pack i took was not valid in Russia. I was even charged for the pack and also the service i used in Moscow. As i couldn't deactivate the number due to business reasons, therefore i had to pay the bill... This is a clear case of cheat, fraud and harassment to a loyal customer. Please help me what should I do.