To sign up for Textline with an existing Twilio number, we'll have you input your Twilio account information (number, Account SID, and Auth Token), and then your Textline account will be created with your current Twilio number.
Select Use Your Own Twilio Account, enter your Twilio account information, and then click Submit. A new Textline Department will be created with your existing Twilio number. This will not affect any voice functionality or any other current use cases for your Twilio number - it will simply route your text messages through our system.
If you are using your own Twilio number(s) with Textline, you will be paying Twilio for your messaging costs, not Textline.