You may at one point want to exchange a coin that Coinomi supports, but Shapeshift or Changelly don't. Unfortunately, our in-app exchange providers do not support all the coins that Coinomi supports. With many hundreds of coins and tokens natively supported in Coinomi, this is understandable. If they provide support for that particular coin or token in the future, it will automatically be available for exchange in Coinomi.
You may also find that a coin that you exchanged before is no longer available on that same exchange. Sending coins from Coinomi is always possible, but when it comes to exchanges, they can be momentarily taken offline for maintenance or upgrade, either by Coinomi or the exchanges themselves.
We're hard at work adding more exchange options, and provide our users with the best rates available.