tariff Plan Change for reliance

Location/place: sus pashan pune

Name of company/service: Ibm India Pvt Ltd

Hi,
I am using reliance datacard(broadband) from past 2 years.Previously i am using unlimited usages plan that my company is approved for us.Now as per our company corporate plan is changed & we have to use the company approved plan.
For changing my tariff plan ,i am chasing(writing mail,calling)from last 5 month but of no use.Still i am getting bill for my old plan,which i have to pay from my pocket.
I fed of writing mail & doing calls to reliance people.Please help me to resolve the same if possible.