If return type is Chat, WhatsApp number is needed.
Country code ( with out + sign ) and Mobile Number
example, the United States number 123–4567 in area code 408 would be written as 14081234567. ( 1 is the country code ). Make sure to remove any leading 0’s or any special calling codes.
As we are using WhatsApp API the prefix + sign is also not needed to add.
Don’t add any spaces, + sign.
for more information — https://faq.whatsapp.com/en/general/21016748