Use Google Sheets to send SMS.

The Sheet SMS add-on allow you to synchronize messages from Google Sheets and to send them using your mobile phone carrier.

Your phone works as a relay for Google Sheets and you can send all the SMS you want.

How to use it : https://youtu.be/7yM8h9tIVs8
The add-on for Google Sheets : https://gsuite.google.com/marketplace/app/sheet_sms/365372815434
More information : https://sheetsms.xyz/