Trying to avoid an exchange

I bought a power bank and had to return it due to a defect. The agent who contacted me was refusing to exchange it because the item returned was apparently missing the charging cord. I told him I don’t remember the item coming with the cord. I asked him/her to check product description of an identical product on their side and he/she was adamant that what I was saying was not true. I had to send a photo of the leaflet that came with the product which clearly stated the product does not include a cable. When the agent realized his mistake, he didn’t even apologize. What’s even more disappointing is that the company gives you less than 2 days to rate the service, so I was unable to rate the agent. I’m absolutely disappointed!