Reliance Trends — Refund related issue

Hi,
I have returned a product in Reliance trends store which was a Juniper kurti sets and worth rs 3399. The person at the customer care have a me a credit note of rs 3399 and told me that the validity of the credit note is till one year.
So after a month of reciving the credit note i went to the store and wanted to buy stuffs worth rs 2000, however at the time of billing the person told me that I don't have enough balance in my credit note. I never used that credit note anywhere or elsewhere before. The customer service representative was very uncooperative and asked my to file a complain online. So it's very disappointing and harassment to me. I waited in the billing counter for two hours and they could not solve my problem. They told me that the store manager is absent .
Can you please help me regarding that.