Yes. You can port non-traditional or VoIP numbers to Twilio as long as they are 10-digit US numbers.
If you do not have an official billing document, you can submit a screenshot of your account page that includes your user name and the phone number(s) included in your port request.
It's important to confirm that the first and last name you provide on the Letter of Authorization match the name in your account profile exactly.
To begin porting your number, please visit the Porting page in the Twilio Console and enter the information regarding the numbers you'd like to port.