Amazon — refunds and return

Sir I bought some books from Amazon
through online mode of payment and return one of them and the refund do not came to my payment account .When I call to Amazon customer care number they told me that refund has initiated. But the refunded amount did came to my account .When again I call them, the told me to contact sbi customer service to tell them the reference number for refund amount, but the told me that they can't help me with any reference number.
Please solve it sir