With the broadcast list feature, you can send a message to several of your contacts at once. Broadcast lists are saved lists of message recipients that you can repeatedly send broadcast messages to without having to select them each time.
This will create a new broadcast list. When you send a message to the broadcast list, it’ll be sent to all recipients in the list who have your number saved in their phones’ address book. Recipients will receive the message as a normal message. When they reply, it’ll appear as a normal message in your Chats screen. Their reply will not be sent to other recipients in the broadcast list.
Note: Only contacts who have added you to their phone's address book will receive your broadcast message. If your contact is not receiving your broadcast messages, check to make sure they’ve added you to their address book. Broadcast lists are a one-to-many communication. If you want your recipients to participate in a group conversation, you should create a group chat instead.
Alternatively, tap Edit, then the "–" icon next to the list you want to delete > Delete.