To message someone not in the address book or my contact list:
- open browser on mobile phone and type (without the plus '+' sign)
- or use my own page
https://api.whatsapp.com/send?phone=15551234567&text=Hi%20there
e.g. https://wa.me/15551234567?text=I%27m%20Gary.
e.g. https://wa.me/15551234567?text=I%27m%20Gary.
Source = https://faq.whatsapp.com/en/android/26000030/
