but, this starts the default sms manager and makes the sms appear already compiled
however, you have to send it manually to be able to send the message
Is there a way to send an SMS automatically without user intervention?
There technically may be a way to do it however if you do & you want to distribute the app via Play Store, you will be in violation of Play Store's policies:
We don’t allow apps that send SMS, email, or other messages on behalf of the user without giving the user the ability to confirm the content and intended recipients.