Reliance Mart — Return not allowed before billing/Refund issue

Address: Plot No. 2, Aggarwal Prestige Mall, Rani Bagh, Pitam Pura, New Delhi - 110034

I recently went to reliance smart rani bagh, pitampura store on 13/06/2020 for purchasing groceries and asked from payment counter if payment can be made from sodexo meal card. They said yes. Then i selected my items which i required and then again i told at billing counter that i need to make the payment through sodexo meal card and what is the total bill amount when they have scanned all my items. They told total is 1429/- then i given the sodexo meal card and they deducted only 879/- and asked for 550/- as cash. I told them that i am not having card/cash since i wanted to use my sodexo meal card for shopping. Then billing counter person told that only food items can be taken from this meal card, i said ok i don't need other 3 items which are not in food category for which i have to pay 550/- cash. They said you have to pay cash else your 879/- amount which is already deducted from sodexo meal card will be waste and it can't be refunded/cancelled and you can discuss at customer care desk after the billing.
Then i discussed at customer care desk that i don't want the 3 items and you can return my 550/- but they told that we can't issue refund but only can give you voucher which is valid for only 7 days.
Since i told them that i don't need 3 items for rs. 550/- before billing so i need refund of 550/- back since i am already getting those 3 items at better rate from other nearby shop. They told we can't do anything now.
Desirable resolution - i request for refund of 550/- and i will return the 3 items. I have attached the invoice copy for your reference.