There is a character limit of 160 per SMS message. If you go over this character count, there will be additional charges.

In the Misc. 5 tab of Maintenance there is a “send long SMS without prompting” checkbox.

If this checkbox is not checked, when sending mass communications such as recalls or marketing, the communications will fail to send if the SMS messages are over 160 characters.

If the box is checked, then the communications will send, even if the character limit has been exceeded, but you will be charged for additional messages.