Click the send TCPA Invite button from the Contacts table.


Then select Send to Imported File and click the Choose File button.  


It will show you how many contacts on the list have valid mobile Mobile Numbers. The sample below shows 2 imports of contacts that have not yet been invited. The 1st file has 4 mobile numbers and the 2nd file has the same 4 mobile numbers plus 2 landlines. Only the Mobile Numbers show up as valid.