This is a question that comes up a bit...
For example, you have your Main Groups: Group A and Group B.
But just want to send to a few people from within Group A, and it's not necessary to create a Group C just for this one-off SMS blast.
Can you select just a few people from within Group A?
Just go to Maintain Groups
Select the Group/s
View the fields to filter further
Tip: "Display Value Fields In Results" may be helpful as it shows more info about the record.
Search Data...the info will display.
Select the people you want to send to....you can actually select ALL Groups and cherry pick if you want to.
We have a You Tube video that shows you what to do.
Click here to view HowTo video