How do you send an SMS from your own software?

There are three ways, with increasing effort and control.

By email

The simplest: your application sends an email to a fixed address, which goes out as an SMS. No development needed, because virtually every system can already send mail. Downside: no direct feedback on whether the message arrived.

Through a REST API

Your application makes an HTTP call and immediately gets a response with a message id. With that you can follow the status. This is the usual choice as soon as SMS becomes a fixed part of your process.

With webhooks on top

With only an API you have to keep asking whether a message arrived. A webhook turns that around: your server is notified as soon as the status changes. That saves needless calls and you know sooner.

What you decide up front

Who sends the message: your web shop, your planning or your CRM? What happens if it fails — retry or alert someone? Those two questions matter more than the choice of technology.