I started a
thread in the Scam Accusation section not too long ago about a problem I had with them. It's worth noting that after I did so, Changelly resolved my problem, more or less. I'd sent an extra 10k sat because I thought I hadn't sent enough the first time, but they never refunded that.
I don't think they're a scam exchange, and I've used them multiple times over the past couple of years with no problems whatsoever. But like a lot of other exchanges, they've got their share of problems and complaints--that's going to happen even with the best of them, unfortunately. I haven't used Changelly since I had the above issue, and I don't plan to, but it's not because I think they'd scam me. They just don't have any coins I'm interested in, and I don't do a lot of trading anyway.
No, they are not totally scam, but selective scamming.
Or it could just be crappy customer service, kind of like the big problem with Yobit. Also, I think a lot of members who complain about exchanges never follow up and say whether their issue was resolved or not. Anyway, I think Changelly is a legit exchange overall.