Going back almost a decade and for some people, Google's Calendar application and service was one of those "must have" Internet services on a desktop or laptop computer. It gave people an interface that wasn't so far away from Microsoft Outlook but was free and ran on most Internet browsers. It was easy to import, export and share calendars, which made the transition from other software packages into Google Calendars easy. Also, Google Calendars had the ability to send text message reminders to their mobile or cell 'phone. This was a free service to have the message sent (although it might not be free to receive the message, depending on your carrier). In a time before the majority of people had at least one smartphone, this was a great service. It meant that you could be reminded of your next appointment without an expensive, clunky and runs-out-of-battery-by-lunch smartphone - looking at Microsoft Windows Mobile here. Even once Android smartphones were introduced, battery life was still substandard for the talk-happy user and many people stuck with their feature 'phone.
In 2015, however, things are different. Smartphone designs have been flattened and slimmed, the interfaces are far more elegant and they have much better battery life. They have rapidly become as prevalent as wristwatches, perhaps more so. And with this in mind, Google has decided to shut down the text message alert service: "Starting on June 27th, 2015, SMS notifications from Google Calendar will no longer be sent. SMS notifications launched before smartphones were available. Now, in a world with smartphones and notifications, you can get richer, more reliable experiences on your mobile device, even offline." There is a note to say that the shutdown won't impact Google Apps for Work, Education and Government customers.
Google's support website details the process for disabling SMS notifications, which is to use the web browser version of the site. Next, users click the settings gear in the top right, clicking on "Settings." Then, pick the Calendars tab and "Edit notifications" for the calendar in question. Simply uncheck the "SMS" boxes, click "Save" and you're done. Customers may also text the word "STOP" to 48368 (United States of America), +447537415730 for the United Kingdom, +34-969-060-900 for Spain, +91-987-080-7071 for India and +1-409-761-1111 for everywhere else in the world (but beware that this last number may be an international number to text the United States of America, so you might be billed as such).
If you are still using a feature or dumbphone and you rely on Google's SMS alerts as part of your calendar, it might be time to consider investing in a smartphone. Seeing as you are already using the Google Calendar and as this is an Android website, might be suggest you take a look at the range of Android smartphones available in your country? You will not have to spend much for an Android experience.