Depending on the length and the characters used in your SMS Content Template, you may be charged for multiple SMS segments.
To do a quick verification, you can paste your message in this tool to get an approximation of the number of segments. Of course, if you are including a URL in the content template, the number of characters created when the SMS is generated will be used and may have to be sent in more than one segment.
1) Open your SMS content template
2) In the Body menu, click on View and select Source Code
3) Take a copy of the content of the Source Code box
4) Open https://twiliodeved.github.io/message-segment-calculator/
5) In the SMS Message box, paste the content copied in step 4
You will see the number of segments, the number of characters that will be sent. Note that if you are using the @Model.TrackingUrl property, it may be longer. You can type in an example here rather than the property to view a more accurate length.
Note: This tool is provided as rough estimate only.