Refused to exchange with bad attitude staff

My husband visited Markham Centurion Mall just a day ago. He mistakenly took Small size underwear. Only he noticed when he arrived home that it was not a Medium size.. Today he went to exchange and they refused to take the underwear. Still packaged as it was, never opened.. The Store Manager too refused to exchange.. Even a blind person could see the package was never opened.. We are not happy with your service and will never buy from the store again.. And yes, i will share my experience with all social media pages..