How to configure Microsoft SCOM to send SMS alerts

Do you have modem that support SMS Protocol Data Unit (PDU) mode?

Steps from Technet
https://technet.microsoft.com/en-us/library/hh212811(v=sc.12).aspx

1. Log on to the computer with a user account that is a member of the Operations Manager Administrators role.
2. In the Operations console, click Administration.
3. In the navigation pane, under Notifications, right-click Channels. Click New channel and then click Text message (SMS).
4. Type a name for the channel, such as SMS channel and optionally provide a description. Click Next.
5. In the Text message box, specify the text that is sent to SMS notification subscribers. The Text message box contains a default message that includes text and variables. You can edit the default message or delete it and replace it with another message. You can click the right arrow next to the Text message box for a full list of available variables. For more information, see How to Customize Message Content for Notifications.
6. In the Encoding box, select the text format for the SMS messages.
7. Click Finish, and then click Close.