You can choose to opt-in a contact for texting using Workflows. This will opt-in the phone number that is in the Phone 1 field and then allows you to send texts to that number.
This option was added to work with VoiceTouch (we call it Messages) and follow up your incoming calls to the system with texts. Here is more about how you might use this: https://help.allclients.com/article/289-follow-up-on-calls-to-your-messages-with-a-text
