Vishal Mega Mart — Return policy

Dear sir/mam,

The policy of vishal mega mart is a scam. I return the product and ask for refund but they said they will provide credit which i have to use in 30 days. But due to some circumstances I cannot used the credit in their mart in 30 days. So they told me that it is expired and cannot claim again.

Why should vishal mart take my money rs1667 simply. If i took any product they can say that I cannot exchange after 30 days but I did not take any product. If all businesses start such kind of scaming like rule, what would you think.
Can I know is this business rule acceptable? Please look into this matter.