Customer asking refund after using the product

[a1masala01]

Dear all
My customer is asking refund after using the Turmeric powder which is order on 12 September and today 29 September she is asking full refund.
What can I do with this type of customer ??
Please advise me.
Regards

[plpmr]

adding to the advice already given -

The fact that you are a registered business seller can make a big difference in giving advice.