So, if what you say is true: you failed providing the offered service (exchanging my coins) so you held my coins for over 150 hours and then charged me all the fees.
After one hour of not being able to exchange the coins and seeing DOGE increased by over 10% you knew for sure the exchange was impossible. So why make me wait 149h more? Why ignore all my messages during that time?
You were unprofessional enough to fail making the exchange; irresponsible enough to hold my coins and ignore my messages for almost one week; and dishonest enough to charge me every fee caused by your errors instead of covering the loses caused by you, without even mentioning the huge lost of profit (more than BTC1) you caused me.

If what you say is not true (which I think is more probable): you saw DOGE increased a lot after the exchange so you decided to hold my coins for several days, sold my DOGE, kept the profit and sent my BTC back charging me every fee. If DOGE had gone down during those days I'm sure I would have received the DOGE instead of my BTC.

We'll never know for sure whether you scammed me or whether you were simply unprofessional, irresponsible and dishonest. In any case I'll never use your services again and would recommend anyone else to do the same.
Anyone interested can read more about this here. You should before deciding to use Changelly's services.