How do I exchange my baby sling?

I purchased a stone small sling last week, I tried it with my 10 month old it was to small, I need to exchange it for a medium. When it was purchased I didn't register with your website. I used my fiance credit card and I throw away the shipping box but do have the cardboard with the hugamonkey sticker logo. Please contact me with information I need to complete the exchange. thank you -alina (mom of two)