I am very sorry to hear that your client apparently are the victim of a hacker ransom attack against your files.
If the files are having an “.axx” file extension, then the files are encrypted with the AxCrypt app only.
However, please understand that AxCrypt is just a tool that is used by millions of legitimate users for good purposes. I am very sad that a hacker has chosen AxCrypt as the tool to perform the ransom attacks.
Unfortunately, in this case, AxCrypt is based on strong encryption, and it is generally not possible to crack the encryption.
What you must do is contact your local police and have them follow the money and Internet trail to the hacker. Since others appear to be in the same situation, you may want to contact media in order to make this problem more widely known, and also gain the possibility of a group action of all the victims against the hacker.
We cannot help, we are in no way involved, and there is no way to open the files without the passphrase used.