per se, this does not comes under unfair practice accroding to RBI guidelines as long as it was informed that the customers wont be eligible for rewards/cashback for particular transactions and the deductions are for those transactions only.
credit card company can always say that they are debiting these reqards/cashback afterwards because of their internal accounting system or whatever.
pls note -- i am in no way defending sbi cards. i myself have got deduction of 1200 on 29th december