Ajio — not refunding money

I purchased s size and then wanted m. I raised an exchange request and soon their delivery agent took the s, but never delivered the m product. For 10 days, i kept getting this info that it will be delivered by 25th jul, but it never got delivered. Their customer care executives do not help and just give false commitments. They close the complaint channel without resolving my issue. They are not paying me my refund even after 8 calls and hundreds of emails.