iPhone users on T-Mobile should hold off on upgrading to iOS 10.
T-Mobile CEO John Legere took to Twitter today to warn customers that a number of users who have made the leap have reported connectivity issues, but a fix is in the works.
Apple is working to resolve the issue with iOS10 for @TMobile customers. Don't download iOS10 if you currently use an iPhone 5SE, 6 or 6+
— John Legere (@JohnLegere) September 15, 2016
The cause of the connectivity loss isn’t clear and does not effect all devices.
If you have already updated to iOS 10 on your iPhone SE, iPhone 6s, or iPhone 6s Plus, T-Mobile says you can temporarily fix the issue by doing a hard reboot.
Apple is reportedly working on a permanent fix that will be available within the next 24-48 hours.