D mart indore - Problem while returning products

Dear sir,

I have purchased a bag of safari and I want to buy blue colour duffle bag but I have wrongly picked red colour, after that I made payment and at the time of checking I found that bag is red in colour. I request the employee to change my bag with blue one, again I made payment for blue colour bag in cash. When I go to return my red bag the employee said that you have purchased the bag with card payment and they were deduct one percent from that payment ,why is it so.I was returning on the same day then why would you deduct .By the way this is an era of online shopping. No body will carry a cash .kindly look into this matter and also worker did not gave us receipt ,atleast you have to provide copy of that receipt.