IIRC there is a way to do this in the settings of mautrix whatsapp, if that’s what you are using.

However, it should only be used if you will be the only user to ever use this server. This is because the puppet accounts will be used for everyone, so if a given whatsapp user is in the contacts of multiple users on your server, and is also in a group chat with both of you, that user would now have two names. One from your contact list, one from the other users contact list.