If you have a mobile number entered for SMS on the customer's record then you will be able to send an SMS text notification from a repair ticket to update the customer on the repair progress.
In order to notify customers about repair progress, you will need an account with SMS Broadcast to enable their API.
You can setup
SMS broadcast API in the settings, by checking the box in front of it and by providing your username and password.
At the moment, the service is available for UK & Australian customers.