Upgraded to iOS 11 iPhone 5S won't connect to data
Disable Wi-Fi Calling. When you disable Wi-Fi and have Wi-Fi Calling enabled it wont connect to cellular data. Not sure if this is related to how T-Mobile Wi-Fi Calling is, or if it is an iOS issue. 

Steps:


Goto Settings
Cellular 
Wi-Fi Calling 
Toggle Off Wi-Fi Calling on This iPhone 
Go Back to Cellular and Toggle On Cellular Data.