How to Schedule Text Messages on iPhone
You can schedule text messages on the iPhone or iPad to be sent at a later time and date. You can automate the process of scheduling text messages with the shortcut app from apple, release with iOS 12.
Get the shortcut app here: https://apps.apple.com/us/app/shortcuts/id915249334
Make sure you turn on background refresh for the Shortcut app inside of your device's setting.
Then, you'll need the actual shortcut for the shortcut app. Get Send Delayed Text Message shortcut here: https://shortcutsgallery.com/shortcuts/send-delayed-text-message/
Make sure to allow untrusted shortcuts in the settings. And if you don't want to use this shortcut, you can use the Yello app.
Here is how to use the Yello app to schedule text messages. https://www.youtube.com/watch?v=Ep4KUx39iDc