Thanks for the post. You could use our SMS API for this task if you want to send the message from the application short code that is assigned to your application. If the same message is sent to multiple users then you could do that by adding upto 50 destination addresses in a single API request. But in the case where the text content is different you would have do that by making 50 separate API calls to our platform. Also understand that there are few things that you might have to keep in mind
The message source address would be the application short code assigned to your applicaiton
You would be able to send messages only to AT&T mobility numbers as destination numbers
You would be able to send only 4096 characters in a single message
It is important that you know that there are limits placed on how many messages you can send in a given space of time. AT&T does this because they want to make it harder for developers to get into financial trouble because "traffic" took off when they didn't expect it. When you are ready to go beyond the limits simply contact The Developer Platform Support team by opening a ticket or by "contact us" and support will put you in contact with a pricing specialist who will help you get what you need!
It is not possible to send mass SMS with your usual phone service because there is the limitation of number of messages on every day basis. This is the reason that businesses are using the extra ordinary text messaging service for business that help them to send out bulk SMS at very reasonable prices. I have also got the app from https://www.heymarket.com/.