Currently, there is no documentation stating that toll-free numbers can be used with the SMS tool. While it looks like using toll-free numbers is not currently possible with the calling tool (source), some businesses fully rely on using toll-free numbers and thus having the ability to add toll-free numbers to the SMS tool would be greatly beneficial for businesses in this demographic.
This would be incredibly helpful for us to have toll-free support for SMS numbers. That is a make-or-break for our business.
Thanks
Agreed, we are facing the same problem here