Amul / Gcmmf — Deducted extra rs. 10 from amul sbi smart change card

Address:

380050

Date of incident: 2nd june 2017
My residence is nr. Avkar hall, ghodasar
I've 2 amul sbi smart change cards. Both were deducted rs.10 on 2nd and 3rd june. They're saying its free of cost and doesn't charge for its services the why deduct the rs.10?
What is the use of smart change card we've to pay for it?
It better to keep change everytime.
Quick response is appreciated.