Paytm Mall — replacement issue

Address:	Patna, Bihar, 800001
Website:	Paytm mall

I have ordered one jacket from paytm and i have received that product on 23rd nov 2018, and now the jacket size is too small and it's not fitting so i just want next size in that, but i'm unable to exchange that product because its not showing any exchange option over there, but it's clearly mentioned 15 days return or exchange policy. I have tried calling customer care but it's not connecting and also i have texted but there is no response from their side.