I am using aritel operator for almost 3 years and a user of its myairtel app as well.
It displays all your usage of calls( local+ std) , msgs and data. And updates on regular basis. The usage gets refreshed at the start of your billing cycle. It is a great idea to have a look on your usage and use it effectively.
However, the data which gets reflected is not correct/right most of the times. It does not get refresh properly after your billing cycle ends and continue to show you unbilled amount based on your next month billing cycle usage. And later when you check you will be get charged extra including excess unbilled amount which was not genuine. And it keeps happening every month. For postpaid users, do check you bills and have a look for the extra charged amount.
I personally call every month to customer care atleast 2-3 times for such app flaws.
This is the reason I do not trust myairtel app.