Go to WhatsApp directly without saving a number in your contact list. It is very handy if you want to talk to a taxi or a delivery driver, someone who call you and asks you to send him a location for example.
Install it on your phone, alow the app to access the clipboard, answer yes to the permission prompts and you're good to go.
This application does not store your data or talk to any third-party servers, all the files are downloaded to your phone and can be used offline, the application is fully open source.