When your current carrier "releases" your toll-free number, it signifies a key step in the porting process. Here's what it entails:

1. Availability for Porting: The release indicates that the losing carrier has made the number available for the winning carrier (in this case, Twilio) to begin the porting process. This is a formal acknowledgment that the number can be transferred.
2. RespOrg Transfer: The release involves transferring the number from the losing carrier's Responsible Organization (RespOrg) to Twilio's RespOrg. This is an essential step before any reconfiguration or routing changes can occur.
3. Continued Service: Even after the number is released, the losing carrier typically continues to provide service on the number for a standard period (usually 10 days). This ensures there is no lapse in service during the transition.
4. Final Porting Steps: Once the number is released, Twilio will proceed with the final porting processes. This includes configuring the number for Twilio's network and setting up routing to ensure the number functions correctly once the porting is complete.
5. Preparation: It's important to have your Voice and/or Messaging URLs set up in advance of the final port date. This preparation ensures that the number will be operational immediately after the porting process is finalized.

In summary, the release of your toll-free number by the current carrier is a crucial step that allows Twilio to take over the number and complete the porting process, ensuring a seamless transition without service interruption.