data usage texts dont match usage on app

The texts I receive from ID telling me I’ve used 80% or 100% of my data allowance don’t match what I am seeing in my account on the app/online. For example, I’ve just received a text telling me I’ve used 100% of my data for this month, but according to the app I’ve got 4.7GB remaining. This is happening every month. What is going on and how do I fix it?