It's not a secret that the rate of any assets is rather volatile and rarely fixed.
Crypto influenced by supplying and demanding from ordinary consumers, investors, traders, the economic and political situation, information field, emergence of new cryptocurrencies and forks and other things inherent to the crypto field and economy in general.
Frequently positive and negative factors overlap with each other with a small time difference, resulting in fluctuations in the rate. Consequently, no one can actually predict or forecast further demeanor with the full confidence. Therefore Changelly is quite restrained with giving any recommendations on buying/selling crypto assets in order to avoid imposing liability.