You attempted to initiate an outbound phone call or message, but the Called phone number you supplied was not a valid phone number. Twilio accepts only 10 digit US domestic and Canadian phone numbers, with or without a leading "1" or "+1", with any combination of character separators. For example, these are all valid: 415-867-5309, 4158675309, +1 (415) 867 5309. You attempted to initiate an outbound phone call, but the
To phone number you
supplied was not a valid phone number.
The formatting of the 'To' number you supplied was invalid.
Twilio accepts phone numbers in E164
[+] [country code] [subscriber number including area code]
You can find a full list of country codes for phone numbers on this Wikipedia page.