Decathlon India private limited - Refund issue

I returned a product on January *rd, **** and opted for a voucher refund, which the website said would be immediate. I received the voucher on January *th. When I tried to use the voucher at a store, the employee said the voucher details were invalid. This happened again the next day. On January *th, I went to the store and they gave me a new PIN code, saying I could use it the next day. On January *th, I received an email confirming my details were correct. However, on January *th, I replied to the email with a screenshot showing that the pin was still invalid. The store asked me to wait for ** to ** hours, but there has been no response since then. I have not received my refund of **** RS and no proper solution has been provided. When I called customer care on January *th, the representative was rude and unhelpful.