If you are a Google calendar fan then this one is for you starting from June 27th, 2015 SMS notifications in Google Calendar will no longer be sent to the mobile numbers.
I just received an email from Google.
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 experience on your mobile device, even offline.
To receive notifications on your smartphone, either configure the calendar app that came with your device or install Google Calendar for Android or iPhone.