The CAYA postbox address cannot be changed - just like an actual address - and this is not necessary. It is linked to your personal customer number and thus your original documents in the archive.
If it happens that correspondence partners do not accept your postbox address because, for example, it does not contain a street name or the postal code is unknown (CAYA uses a so-called large recipient postal code), you can find more information here:
CAYA has its own postal code, which is why systems sometimes cannot match it. If you have problems using your postbox address, you also have the option of using an alternative structure. You can find it in the following article: My Postbox address is not accepted, what can I do?