If you phone connection ain’t working through your hummer or any other vehicle it’s not your vehicle but a nation wide cell service outage from ATT.

https://www.khou.com/article/tech/at...b-38e1acf785f3

 

National service disruptions are unfortunately out of our hands as users. I hope engineers can identify and resolve the root problem quickly to restore normal service for all affected customers. In the meantime, staying connected however possible is important for work and personal use.