You have a maximum of 1600 characters available to type in Chatavise. Every 160 characters will be broken into a new message segment, and you can send a maximum of 10 message segments. It's possible that certain carriers will break up message segments into separate text messages when it's sent to customers, even if it shows as one full message in Chatavise.
What happens if you hit the character limit when sending a text?
Whenever a message is sent with 1601 characters or more, the carrier blocks the message, showing up as a failed message on the Chats page.