Aizaz Imtiaz Awan
Sorry to say but right now according to the available alternative Login mechanism under the Theme Settings, there are only three options available right now which are Facebook, Google and VKontakte. For them the option is available under the Theme Settings > API Integrations > Social authentication: https://snipboard.io/2BO9tQ.jpg
So, if right now you are using any third party Plugin for that, then you would need to contact the respective Plugin Support in this regard or if you aren’t using any third party Plugin right now then you might need to look for a third party Plugin in this regard because as you know the Login/Registration is handled by WooCommerce, so there isn’t a default functionality available for the WhatsApp from their end too.
Hope you can understand !