Airtel — not changing my postpaid plan

My airtel corporate no. [protected] was having a plan of 499/- per month., now this plan was not suitable for us as most of the data was not used by us and get wasted at the end of month. We requested to reduce plan to 199/- but they ask me to send mail from registered id. I did the same i send mail from my registered id and i receive monthly bills also on my registered id. But they might not have updated record or they are reluctant to reduce plan i dont know the reason but they refuse to reduce my plan.
I am answerable person to my company as i do the payment and later send bill for reimbursement.
I have no option and i am not getting any help from airtel as well.
It is requested to interrupt in the issue so that it can be resolved.
My registered mail id s. [protected]@hpcl.in