I have made a lot of exchanges with different coins on changelly before and i never got any issues with them, the only problem there is that they charge unexxpected fee to process exchange through their platform, however i would still say changelly is more cheaper than regular wallet like coinbase, btc.com but as your topic is to know trusted exchange service, i think we have guarantee for our coins safety when it comes to a huge amount, whether it is shapeshift, or changelly, you should exchange in splits, not to send whole amount in single transaction if funds are huge