1. Open Settings.
2. Click on Battery.
3. Click the DETAIL button.
4. Look for SMS Tracker in the list of apps and click on it.
5. Select "Turned off" from the list.
Click here for a walkthrough tutorial
Users running Android 6.x on HTC devices should click here for a tutorial on managing HTC power settings.
Users running Android 6.x on Huawei devices should click here for a tutorial on managing their power settings.
Users running Android 7 on a Galaxy S7 device should click here for a tutorial on excepting SMS Tracker from Power optimization.
Users running Android 6.x on a Galaxy S5 device should click here.