was surprise seeing this. changelly is not a scam. they are 100% trusted, you can go ahead and buy from them if they have bitcoins to sell but if they don't you can try from other sites as well.
I don't know if you have read that they have the power to confiscated your coins if they deem it's dirty. And far as I as know they are requiring KYC now.
Or you can also read this thread,
https://bitcointalk.org/index.php?topic=4619534.0.
You can also read their terms here:
https://changelly.com/terms-of-use