Although I'm unsure of how these appear, I'm positive they're a deception. I doubt that you will simply receive a text message informing you that you have some bitcoin and that all they require is your identification and other documents because you recently transacted with them. I'm not familiar with this website, but it seems odd to me even if I see that several of my friends claim it's for bitcoin transactions. There are other ways to do bitcoin transactions, so you need to cease using these websites immediately. In my opinion, these things could be a hoax. Because what you said seems unusual to the majority of us, and I feel that if it were true, someone would have discussed it here. Once its legitimacy has been established, you may come back and use it again.