How to file consumer complaint against network provider?

I am a loyal customer of Vodafone services since 3 years. I converted from Prepaid service to Postpaid in Aug 2014. Since past 6 months, I am trying in vain to convert my number back to Prepaid but each time that I go to their store/call customer care, I am given some or the other excuse. Last month I prepaid my bill. This payment was not updated by the store executive & so my sim was deactivated even though I showed the receipt to the store rep & also to Vodafone via email. A lot of heartache has been caused to me. I want to file a complaint in Consumer Court against Vodafone. Please help.