Myntra - Can t Exchange to a lower size due to insider points

I have bought a jacket from Myntra and want to exchange it with a smaller size but option is not available since I have collected the points. Speaking to their customer care people is not helpful.neither they are providing any escalation Matrix nor trying to help. All they have same answer that it's irreversible . So I want to know what kind of privilege customer membership they are giving when customer can't exchange the clothes. They can take their point back and give me an option to exchange the jacket but they are telling they can't do anything. When I asked to opt out from insider program they can't help. They are forcing me to become an insider member.where they can run this kind of fruad programs