Is it possible to use “File Uploading” for sending SMS to a large group?
Yes, but not more than 500 messages each file.
*** “File Uploading” is the best way to send SMS to a large number of recipients ***  
This can be done by using Microsoft Excel. Each sheet contains up to 500 phone numbers and 3 columns of information. The first column is destination phone numbers. The second column is “#”. The third column is the content of messages. It is suggested to put your phone number at the end for testing. Then save as this file with .txt extension. You can now upload this “.txt” file to send messages. For next time, you can use the same file and edit content with “replace” command.
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