Call us at 713-207-7777 or 1-866-222-7100 and provide the call center agent your mobile number. A triggered text message will be sent to your mobile device. Be sure to reply "YES" to 697697 within 2 hours of receiving it to subscribe. The call center agent can also help you select which particular text alerts you want to receive.
You can also opt-in through your online account. Once logged in, choose "I want to manage my profile" from the dropdown menu, then "Alerts & Contact Preferences." From here you can choose which text alerts you want to receive.