The question is why does it take about 20 days? Either there is a rule to prevent sending money to any one-time address and thus lose your money or the response of the support team be faster?
As long as the support team can access the private key for that address, then why does the support team not send money to the user because they will be able to recover it at any time.
If the support team cannot access the private key, inform the user about losing his money.
Why the delay?

Generally, Changelly's Terms of Use 2.6.3 indicates the laziness of the technical team. It is easy to reprogram the system to verify RBF or the possibility of receiving funds several times at that address.