Vodafone India — Fake call

Address:

Bangalore, Karnataka, 560071

This is manjunath i’m a government employee working in isro.
My mother using vodafone postpaid connection for more than 5 years now and i have paid all my bills on date till now.
My current plan is 99rupee and usually will get a bill of 150 to 250per month.

Last april month i got a vodafone bill of rs 4200/- and was really shocked to see this much amount. Since i m sure that my mother had not used so much, i called cc of vodafone they said will check and get back within 3 working days. And today when again i called they confirmed that it was a valid call and an isd call was done which was charged for rs 4200 for 35mins.
Since my mother never do any isd or even std call i asked them for the details, i’m mentioning the details in the last.
Then when searched my mother call log nothing was there bcoz it's a basic mobile, after twice i requested vodafone care they sent itemised bill then i came to know isd call number in the bill.
Now after doing some research i came to know that this is some hacking thing done by some fraud ppl for money.
Now i have a question, how this is a valid call? How can a call be charged for 4200 rs for 35mins?

Since it is a fraud call, these kind of calls should be blocked or added to the spam list from network company (Vodafone).
I’m not ready to pay this extra amount (4200), as my mother not done any mistake to pay this much amount for a fraud call.

Can you please provide me a solution to handle this situation?

In case if i have no other option other than to pay the entire bill amount, i would be very much happy to disconnect this vodafone connection and will never use it as this is not at all safe (Remember people like me might not be aware of the fraud numbers and it is the responsibility of the company to take care of this. Or incase if mistake like this happens then that amount which ever has been charged should be waived off)

Waiting for your reply as the last date of my bill date is over and number also disconnected/ suspended

Details of the call,
Number : [protected]
Charge : 4200 rupees for 35mins

Thanks & regards,
Manjunath