What is a "lookup" and what triggers one?

When you send a text message to one of your end users TextPower tries to make it as simple as possible.  You send it to us and we do the rest.  In reality, though, it's not simple at all as there are many steps along the way.  One of the key pieces of information required is knowing whether that number is a mobile or landline.
There are essentially two ways for TextPower to obtain this information.  If the user sends a text message to us with a keyword, for example, we can assume that the sending number is a mobile.  We then opt that number into the opt-in list for that keyword.  
If, on the other hand, you upload a list of numbers using, say our Communications Assurance Program (CAP) that facilitates an expedited means of getting tens of thousands of numbers in the database for your exclusive access, it must be determined whether those numbers are mobiles or landlines before the opt-in can be completed so we put them through a "lookup" process.  
Virtually all of the cellular phone companies in the country participate in what is known as the National Cellular Database.  Even most rural cellular carriers and Google Voice numbers are available through this database.  This centralized and master compilation contains not only the number for every cell phone, it also has the information about which carrier services it.  The lookup process accesses this database to determine whether it is a mobile.  If it is, the mobile number is then opted into our system in the same way that as when the mobile user sends a text to our system.
Carriers charge TextPower for these lookups when numbers are opted into our system via a list upload and so we are compelled to charge for them.  Only when new numbers are added to your service will you be charged for a lookup after the initial opt-in processing.