Airtel — charge against link aadhaar with mobile. no

Address:

Faridabad, Haryana, 121003

Dear sir i link my aadhar with mob number [protected] in a airte store, why i charge of 50rs for it when charges are not aplicable for it. I asked the airtel exicutive he told that service is chargeble with rs 50, airtel store is in sarai khwaja near govt school faridabad kindly suggest me why linking charges are being taken from costumers i recieve this massage after payment you have paid rs.50.0 to merchant no [protected] using airtel money.. Txnid:[protected], bal: rs. 50.00.