Welcome to the community!
From the screenshot you provided it looks like you are viewing the talk and text details on your account so the data portion should not be displaying in that section that's why its showing that error message.
Did you recently made any changes to your plan? You can wait until your cycle resets and see if the details displays properly if not I would suggest you contact customer service and they can look into it further.
You can always reach out to customer service through any of the available methods listed here.