Charges for unconsumed data

Dear Sir/Madam,

For the last two months I have been charged for using mobile data with my one of my SIM. I am sure that I did not use any data since I am using a data disabled phone.

I believe it is done by mistake and I kindly request you to credit my bank account with the charges. If this is going to happen again then I will have to take action.

For safer side since last week I am using an old phone which is not data capable (Old Nokia).

Thanks and best regards,
RR