Tossable Digits is an option. They state "As of July 2018, we have tested and you can use our Virtual Numbers to verify WhatsApp and Viber accounts using the "C

Tossable Digits is an option. They state "As of July 2018, we have tested and you can use our Virtual Numbers to verify WhatsApp and Viber accounts using the "Call Me" method. The SMS option does work with a US Short Code as well. You may need to wait 60-120 seconds after you try to send an SMS verification code in order to have the Call Me option begin." Not sure it still works, but it is an option. $3.49/month for the number with unlimited SMS and Voicemail, plus SMS Short Code support.