Airtel — linking of aadhar number to mobile no-reg

Address:	Tiruvannamalai, Tamil Nadu, 604202
Website:	airtel

Airtel has mentioned that linking of aadhar number to mobile number is done at free of cost at airtel centres. But it is not so. On 17/10/2017 i visited a airtel centre (Opposite to state bank of india) in gingee-604202 to link my two airtel numbers. They have charged rs.20 for linking the aadhar with my mobile number. I asked them airtel has mentioned that it is a free service why charge
Rs.20. But they denied and recevied rs.20. The same day i have contacted the airtel customer care complained. Till now no response. Is airtel ecncouraging this?

The airtel centre name is bismillah agency (Opposite to sbi)