Issue in Billing

Location/place: Santacruz West (Juhu)

Name of company/service: Housewife

I have been using Vodafone number for over 10 years now.. Have always cleared their bills without even monitering them in the last so many years.. Have started mointering their bill for the last 3 months and every time have found an issue in billing.. last month bill sent to me was of rs 7000.. out of which i agreed to pay rs 4000 and rs 3000 that they claim is for mobile data I havent used that.. I am in discussion with vodafone guys but they denying the fact that i havent used the mobile data.. please help me resolve this.

thanks
namarata