Yes, you are able to turn off text notifications within the TRUX app. This will not turn off notifications if you were specifically request for a particular job.
To do this, you will want to the Menu within the app and click "Go On Call"
This will pull up a list of trucks and by default, all will be turned on. If you wish to stop receiving notifications, turn each one off by sliding the circle to the left. This can always be turned back on at any time.