Hello, sorry for the delayed response, I missed your post earlier. Regarding the language override issue, I’ve tested it and it works. There are two MOD_WHATSAPP_AGENT_MAIL_NAME_LABEL strings there; are you sure you have translated both of them?
Alternatively, for a cleaner solution, you can translate the file: /language/en-GB/en-GB.mod_whatsapp_agent.ini.