I have confronted Changelly about this. I sent three emails filled with charts showing the price of Bitcoin at the time of my transaction, calculations using Changelly's posted fees, and requested proof from Changelly (i.e., screenshots of charts, as I provided to them) of the price of Bitcoin at the time of my transaction.
Here is Changelly's response:
<Slightly higher rates? SLIGHTLY HIGHER? In other words: we have your money, you can do nothing about it, and we won't do anything for you.>
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Today, I went to Crypto-currency Market Captitalizations; the price of Bitcoin was $906.27 USD.
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I also went to Bitcoin at BitcoinWisdom immediately thereafter; Bitcoin was $903.03, at that moment.
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Additionally, I checked the price of Bitcoin at CoinGecko; the price of Bitcoin, at the time, was $900.1588 USD.
Did you notice the "Buy Bitcoin Instantly" button? This is a direct link to Changelly! I clicked that button. This took me to the Changelly screen to purchase Bitcoin. I entered 15 as the amount I wished to purchased (as in my actual transaction) and here is the screen as I saw it at that moment:
Note the amount of Bitcoin to be received with $15 (0.0122258).
This represents an ABSURD EXCHANGE RATE of $1,227.2366 !
This is NOT anything close to what any of the above charts represent and CERTAINLY NOT $900.1588 as shown at CoinGecko!
If one was on CoinGecko and clicked the “Buy Bitcoin instantly” button, one would expect (at least close to) the rate shown on CoinGecko, regardless of which kind of funds were to be used. Unless one did the math, one would not know one is being charged up to 26.67% in this case < in other words, "ripped off">. Then, Changelly will deduct network fees and commission on top of this . Their stated commission is 0.05%.< hmmm>
How many of you clicked on that button at CoinGecko and thought you were getting the price shown there when you made (or almost made) an exchange at Changelly?
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How many of you actually looked at the transaction in the blockchain to try and figure out what happened?

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As I stated in my previous post, in my case, the highest chart price when my transaction occurred was ~$924 USD. The exchange rate shown on my receipt was ~$1,761; a whopping 52.47% difference! Then I had to contend with the fees on top of that! I felt I was ripped off!
How can Changelly justify these kinds of differences? Why is there such a fluctuation in the exchange rate percentages?
As I was writing this, I was wondering which exchange they use for transactions. They say they search to find the best exchange rate, but their search seems nearsighted. Rather than admitting to absurd fees for exchanging USD fiat for bitcoin, they seem to be using an exchange with ridiculously high exchange rates. I have asked for the website address to the bitcoin exchange Changelly uses so I can clarify my transaction. As soon a I get a reply, I will post it for all to see.
Does anyone know what exchange Changelly uses which would account for the absurdly high exchange rates? Why would the bitcoin exchange rate be so high when using fiat rather than any crypto currency? I can understand charging a nominal fee to exchange USD fiat to Indian(?) fiat (rupees?), then a fee to change fiat to bitcoin. Of course there's the network transaction fees and commission - which are posted. Such fees should be clearly stated. Still, this should not amount to over 50% of the initial amount. What about seeming to HIDE FEES IN AN UNCLEAR TRANSACTION AND EXORBITANT EXCHANGE RATES?!?
Perhaps Changelly would like to be introduced to another exchange platform without such high exchange rates? < riiiight. wink, wink>