Sell.com Cash my cell phone Usell is a complete scam Internet

I was quoted $160 for my damaged iPhone 4s. I accepted the offer and they sent me a pre-paid envelope a few days later. One day after receiving the envelope, I sent my phone to them. That was over two weeks ago and I continue to get emails from them saying they have not received my phone. I wrote to find out the status about a week after sending the phone in and they replied asking me to send them all of the details they should have already had like device type, condition, etc. I replied with all the info they asked for but never received a response OR a payment. I've since sent them 3 or 4 follow up emails and each time I get the automated acknowledgement saying they will contact me within 24 hours but I have not heard a peep.

Do not send them our phone if you want to get paid. They are a huge scam. Anyone who wants to start a class action against them, please sign me up.