Vodafone India — bill dispute

I am using vodafone services for more than 5 years. I have been paying the bill amount regularly.
As my mobile became defective, i have started using my son’s mobile phone.

I suddenly received a bill for more than rs 4500. Vodafone informs me that i hv exceeded the plan data and it is billed + unbilled amount.

I have explained them that i am 77 year old senior citizen and have no idea of data usage.
Unknowingly i might’ve kept the mail data on all the time. I visited their gallery and they advised me to write to their consumer service for possible reversal. I requested them to reverse the bill amount.
Vodafone is not considering my request.
Please do the needful for reversing the bill amount
Regards
Hariharan