The basic function of calling on the blue button only involves a Verizon cell phone call to an 800 number.
All of the "digital" features like checking battery status, remote start, remote unlock... Are not reliable. It does not matter if you are talking about an iPhone app. An Android app. The MyVolt web site. A Volt. A Cruze. A Suburban... ALL fail to work reliably with on the OnStar digital features. This is an OnStar server/network issue.