OS Services Booking supports SMS Sending when orders is made. There are various SMS types like Order notification, Payment notification, Booking reminders...etc to customers, administrator, employees

You can configure content of SMS through tab: SMS Setting in OS Services Booking Configuration

Moreover, OS Services Booking supports below SMS providers:

They are plugins of component, you can find them at Backend -> Extensions -> Plugins. To use one SMS provider, you should enable the corresponding plugin and enter valid credentials for them

The most popular SMS provider is ClickAtell. You can read about How To: Get Clickatell API ID through this documentation: http://joomdonationdemo.com/osservicesbooking/documentation/integrations/clickatell