There is no fee to port a number with Twilio, and once you port it in it is $1/month to hold onto the number. To port, you log into your Twilio account and visit the phone numbers tab and select "port number", or hit this URL
https://www.twilio.com/user/account/phone-numbers/porting
At this point, you fill out a form asking for the billing information and then we follow up with you to get authorization to transfer the number (usually just a signature). It usually takes about 10 business days to complete the port.
At this point, you fill out a form asking for the billing information and then we follow up with you to get authorization to transfer the number (usually just a signature). It usually takes about 10 business days to complete the port.
(I work at Twilio too)