Self-serve usage history is the only way users can track their usage. There are no bills or emails atm where they can do that. For sure it is barely used by users who rarely texts, calls or use data, but those wanting to find out incoming text or call number or calculating data usage, it would be a handy tool.
The usage history combines texts, calls and data all together. There are very less rows show up with pages after pages. So, it is not easy to track your text, call or data usage history if you don't remember the date correctly.
It allows you to generate history for past 7, 30 or 90 days. Public Mobile should implement similar drop down options like "Texts" "Calls" "Web", that will allow users to generate text, calls or data individually. I think this is not very difficult to do from the programming point of view.
Alternatively, if possible, they should allow users to generate excel spreadsheet or other file formats where users can sort out history however they like.