Finally, your app users can able to send you WhatsApp message without saving your number in his contact list.
Just use below code and when user will click on it, he will be redirected to your WhatsApp chat.
Go to Features >> Custom Page >> Add Text Section >> Click on Source Button
<a href="#" onclick="window.open('https://api.whatsapp.com/send?phone=91XXXXXXXXXX', '_system', 'location=yes'); return false;">Click to Chat</a>
Note: here you don't have to use 0 or + sign in country code. For INDIA, Country code is 91.
Just use below code and when user will click on it, he will be redirected to your WhatsApp chat.
Go to Features >> Custom Page >> Add Text Section >> Click on Source Button
<a href="#" onclick="window.open('https://api.whatsapp.com/send?phone=91XXXXXXXXXX', '_system', 'location=yes'); return false;">Click to Chat</a>
Note: here you don't have to use 0 or + sign in country code. For INDIA, Country code is 91.