Adding SMS Quickly

I am completely new here and not good in programming. I have installed nextcloud and it is working. I would like to send SMS to users in the everyone group when an announcement is sent. I have enabled announcements and I am receiving emails.

My question is, which specific function sends emails to users in the Announcement APP.

Kindly direct me to:

  1. where the php file is ( is suspect apps/announcementcenter/lib/Notification/Notifier.php)
  2. The specific function that sends emails

I think from there i can use an API of a mobile service provider and send sms when an announcement is made.
Note: SMS Relentless looks very good but for folks out here in africa, using the providers from US is very expensive, almost 20 times more expensive.