Welcome to the Community!
Are you looking at the data usage through the Fido My Account app or through the built-in data tracker of your device?
The information on the app will reset automatically on your billing cycle date .
If you are using the built-in data tracker, then you might have to set up the correct billing cycle date (Android) or reset it manually every month (iOS).
Can you tell me which device you are using? Also which tracking method you are using?
Is it the Fido app or the built-in tracker?