Hypd - Won t exchange a jeans for the size

Purchased a jeans of size **.. wanted the next size and since it was my first time shopping,I wrote to their "contact us". It was said they will get back so I presumed I shall get a call back..which never happened.. wrote to their insta page etc and then they informed they had sent the mail... which they did..and I in return told them about the size.. Their next mails suggested,I haven't mentioned the size.. but I did . By the time they got back..it was over * days. ( their exchange is * days) so they said they have limitations and won't exchange the product.. however in the net I saw that their return is ** days from the purchase.. I just want next size of the jeans I purchased . Which they are not ready to do