Sending text message notifications using Alma data, requires coordinating with a texting platform and service. When implementing, I highly recommend using an opt-in model for SMS messaging, allowing patrons to agree to any associated costs.
Alma sends any applicable SMS notices (see link below for available notices) to patrons who have a preferred mobile phone number in their user record. These notices are sent in periodic batch jobs via SFTP to a server. Your texting platform then communicates with that server, picks up the file, and notifies patrons at their preferred mobile phone number for the applicable notices. There is a nominal cost to this process arising the from the texting platform/service.
Not all of the user notices are available to be sent via SMS, Ex Libris covers which ones can be sent here: