I don't usually use these exchange apps, I like going to their main website and trade there on my own. I find it that there were times that apps causes bugs when I was using them that's why I've never used them again.
- Changelly - it's new, I don't know if it's stable and well-working, and there are not enough reviews, but I was satisfied with the web version though
They have an active account here that has negative reputation, you should check it.
Username:
Changelly