Since you spoke with customer service, I assume they had you reset it.
I had an issue with a right-click button that didn't always work and was ready to send my Kobo back, but I called customer support and they walked me through a reset. To my surprise, that seems to have fixed the problem.
It's very frustrating for a new purchase not to work and I don't blame you for wanting to send it back. You never get the chance for another first impression, as they say.
Then again, there's the other cliche, about the two people who meet, hate one another instantly, and eventually fall in love.
I hope the Sony works out better for you!