Helite Zip'In 2 Equestrian Airbag Vest Medium

EUC Helote Zip'In 2 Equestrian safety airbag vest size medium. purchased a couple of weeks ago from original owner, who only wore it a few times and needed to go to the next size up. I received it in the mail and realized I need a size small so just trying to get my money back so I can purchase a small. Unfortunately, because Poshmark will not allow me to adjust the shipping, I will be unable to ship it with the air canister.