Deploy messaging promoting WhatsApp on the company website and in email signatures using wa.me links; such links automatically connect the business with the customer via the latter's phone number. Also consider raising awareness using organic SERP (Search Engine Results Pages) listings for the Contact Us page, and campaigns with Google Ads.
Promote the WhatsApp channel on product packaging and in advertising such as on billboards or in press ads, preferably with QR codes that can be scanned by the customer in an instant. Also consider IVR phone deflection that enables companies to integrate WhatsApp Business within an IVR tree, and deflect incoming calls to WhatsApp.
Have a look at all ideas to increase your WhatsApp presence here.