Sorry but I found this app complicated. The other apps that are out there have much better segment options and I can create specific list. On this app you can only segment customers, but you can't create a list of it. Then you don't know how many people you have in the segmentation so you don't know the cost of sending out the text message. I been in contact with their support but they don't get what I mean. Sorry moving on.
Here's Raymond from FireApps Customer Support Team, and we are truly sorry for this inconvenience caused.
Regarding your concerns, I would like to confirm that you surely can create any specific list as you want.
Once you have done your segment, please go to Contact => "Add Filter" Segment, then you can view number of customers/contacts with details information in this segment, and of course you will know the estimation cost of sending messages.
In a specific case, if there is no contact in your created segment, the estimated cost will not be updated.
If you have any further concern, please feel free to contact us via our live chat, or email at firstname.lastname@example.org