WhatsApp messaging doesn’t necessarily need a mobile number to work, at least for this variant of the app. WhatsApp Business app allows them to register using a landline number. WhatsApp is only available on Whatsapp for Business app and not the regular app that consumers use. The use of landline for WhatsApp is different from connecting via a smartphone or even a feature phone, both of which have a screen.
Post that, WhatsApp will try to verify the number first by SMS. When that fails you can select the ‘Call me’ option to get the six-digit one time password (OTP) to start using the platform.
For those asking why doesn’t WhatsApp offer this feature for regular users, recent figures have shown that the number of mobile users in the country are far more than landline subscribers. With falling data rates, free SIM and voice calls, the difference is only going to become wider.