[Resolved]  D-Mart/undergarments — Exchange

Dear sir,
I have purchased undergarments from the above mall(D-mart), But by mistaken i chose wrong size of it. Again the bill was destroyed by me. And ask them to exchane it, but they are refusing it to do the same.
I know that they have records of bills in there computer, but they are saying that you should come at time given by him. But i am doing a job, so it is not poassible to go there at the time specified by them.
So can you answer my question?
What the malls are doing with customer is justice or not?