Respected Sir/Madam

I am using Airtel Gprs service which says I can use Facebook through Airtel Live till 31st of August without charge. But on 12th of August they charged me Rs.151.80 .I had an initial balance of Rs. 197.47 and I am left with Rs 45.67.
I called customer care and they first told me that they will not refund money because I have downloaded some videos and browsed some other sites which I have not. They were making excuses. Then I talked to some of their senior at 9818334865 but the lady on the other side told me that they will only refund Rs. 70. But I refused by saying that I want my whole money back. This is unfair.
I don't know what kind of policy they have that they will refund me less than half of my money and that after when they are at fault.
Last week also they deducted Rs. 28.30 but they refunded me than and now they are making excuses.
Kindly look into the matter and resolve as soon as possible.

Yours sincerely
Rahul Hasija
WZ-89,Old Sahib Pura
P.O. Tilak Nagar-110018
9971038081