Welcome to the community!
Sorry to hear you've incurred data overage charges. I understand it's 2022, but it appears as though you might have an older plan. Most of Fido's newer Data, Talk & Text plans include Data Overage Protection. With the older plans, the most recent overage rate was $10 per 100MB. As far as I am aware, one of the current Basic plans also has the same overage rate, which is less than the current rate from other providers.
Unfortunately, overage data has always been more expensive than regular data. While Fido doesn't stop data on plans without Data Overage Protection, they do provide a means to monitor your data usage via your My Account.
Hope this helps 😀