Mr A.

Many sellers on Carousel are scammers because they can get away with it as the site is not policed.
They advertise items such as mobile phones very cheap and encourage you into paying for it using an insecure form of payment. Then they stop contact and the item never arrives.
No way to get your money back.
No way to directly contact anyone in Carousel for assistance.
No way to talk to Carousel staff.
When you report an incident through their messaging system nothing happens.
Even if you were smart enough to pay via PayPal and mark payment for goods to get your buyer protection it takes 3 weeks to get your money back.
My experience is not a one off. I have witnessed scores of scammers on Carousel. Even one that scammed me yet Carousel did nothing despite multiple reports and complaints. The scam account is hence still active.
There are a few genuine sellers but many of the listings are months old as the system does not automatically purge old listings.
This site is hence HIGH RISK! FORGET THIS SITE!