Hi @oldernweisser!
My apologies for the frustration you’ve experience with the application and the data usage manager!
What kind of phone are you using? We would be glad to help out!
Sometimes after an update you need to clear the cache of an underperforming application to get it back to par. With most Androids you can do that by going to Settings > Device > Applications > Application Manager > MyAT&T > Clear Cache and Data.
As far as your data usage manager, is it no longer selectable? Running on my own 6.0 device, it is selectable within Settings > Quick Settings, as well as Settings > Connections.
I hope you find that helpful! Please feel free to ask any more questions. We’re happy to have you here in the forums!
Tim, AT&T Community Specialist