Drupal 6, Ubercart, SMS notifications

Hello everyone, dear developers and programmers!
I am one of the developers of the "SMSC Access" team for sending SMS messages and mailings.

There is a question: there is a Drupal version 6 installed, on which Ubercart version 2.17 is also already installed.

It is required to write a module that would send messages through our service when the order status changes.

The module currently implements authorization, service testing (test messages), and creation of text templates (table smsc_templs).

No one on our team has worked with Drupal before, hence the question: how to make it so that when the order status changes through Ubercart, a function to send SMS to the number specified in the "phone" field on the order page (in the cart) is called.

At the same time, there is no possibility to edit the Ubercart module. Using SMSFramework is also prohibited.

While studying Drupal, I encountered the concept of "hook," but I did not understand how to use them correctly. This question is for all who know.
Who can help and who will need an SMS sending module, I can assist later.

The result should be a module that you simply install in Drupal 6, authorize, create a template for each status, after which when Ubercart changes the status it triggers our module and it sends a message about the order status change.