If you have a phone number entered for "SMS phone" and their carrier selected in "SMS Carrier" on the customer's record then you will be able to send an SMS text notification/alert from a repair ticket to update the customer on the repair progress.
To send an sms with the repair status click the sms notification button (the one with the bell icon) on the ticket view screen.
The text it will send to the customer's phone will read like this:
[customerName], your [deviceName] is [ticketStatus]. Call with questions at [locationPhoneNumber].