Can I write my company name instead of my phone number in WhatsApp
In order for customers to see your company name and not your phone number, you should install the WhatsApp Business App (not to be confused with the WhatsApp Business API).
This is the official free application that has advanced functionality when working with the messenger, including the ability to edit the name of your company.
WhatsApp Business App has other useful advantages, such as segmenting the contact base by color scheme, sending "goods", auto-replies. These capabilities are also available in the Chat API. You can find them in the sections of the documentation.