These websites are a trap. You send them your phone, and once they have it, you are not getting it back under any circumstances. They will pay you only 50% of its actual worth.They don't return emails till you get tired and pissed of mailing them.
Moreover, it takes long time to get to their customer support guys...Just spend some time looking on the websites and you will wonder that they are still working smoothly. I would never recommend their sites to anyone